diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5dc32e7a..c346c4f4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Changed
 - Update test case to current (PHP) standards ([#831](https://github.com/jsonrainbow/json-schema/pull/831))
+- Upgrade test suite to use generators ([#834](https://github.com/jsonrainbow/json-schema/pull/834))
 
 ## [6.4.2] - 2025-06-03
 ### Fixed
diff --git a/tests/ConstraintErrorTest.php b/tests/ConstraintErrorTest.php
index 158f3074..cc599010 100644
--- a/tests/ConstraintErrorTest.php
+++ b/tests/ConstraintErrorTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests;
 
@@ -24,7 +19,7 @@ public function testGetInvalidMessage(): void
     {
         $e = ConstraintError::MISSING_ERROR();
 
-        $this->expectException('\JsonSchema\Exception\InvalidArgumentException');
+        $this->expectException(\JsonSchema\Exception\InvalidArgumentException::class);
         $this->expectExceptionMessage('Missing error message for missingError');
 
         $e->getMessage();
diff --git a/tests/Constraints/AdditionalPropertiesTest.php b/tests/Constraints/AdditionalPropertiesTest.php
index 46b29a82..a4753cde 100644
--- a/tests/Constraints/AdditionalPropertiesTest.php
+++ b/tests/Constraints/AdditionalPropertiesTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -15,10 +10,9 @@ class AdditionalPropertiesTest extends BaseTestCase
 {
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
+        yield [
                 '{
                   "prop":"1",
                   "patternProp":"3",
@@ -49,8 +43,8 @@ public function getInvalidTests(): array
                         'context' => Validator::ERROR_DOCUMENT_VALIDATION
                     ]
                 ]
-            ],
-            [
+            ];
+        yield [
                 '{
                   "prop":"1",
                   "additionalProp":"2"
@@ -62,8 +56,8 @@ public function getInvalidTests(): array
                   },
                   "additionalProperties": false
                 }'
-            ],
-            [
+            ];
+        yield [
                 '{
                   "prop":"1",
                   "additionalProp":2
@@ -75,8 +69,8 @@ public function getInvalidTests(): array
                   },
                   "additionalProperties": {"type":"string"}
                 }'
-            ],
-            [
+            ];
+        yield [
                 '{
                   "prop":"1",
                   "additionalProp":2
@@ -88,8 +82,8 @@ public function getInvalidTests(): array
                   },
                   "additionalProperties": {"type":"string"}
                 }'
-            ],
-            [
+            ];
+        yield [
                 '{
                   "prop1": "a",
                   "prop2": "b"
@@ -100,8 +94,8 @@ public function getInvalidTests(): array
                     "type": "boolean"
                   }
                 }'
-            ],
-            [
+            ];
+        yield [
                 '{
                   "prop1": "a",
                   "prop2": "b"
@@ -110,14 +104,12 @@ public function getInvalidTests(): array
                   "type": "object",
                   "additionalProperties": false
                 }'
-            ],
-        ];
+            ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
+        yield [
                 '{
                   "prop":"1",
                   "additionalProp":"2"
@@ -128,8 +120,8 @@ public function getValidTests(): array
                     "prop":{"type":"string"}
                   }
                 }'
-            ],
-            [
+            ];
+        yield [
                 '{
                   "prop":"1",
                   "additionalProp":"2"
@@ -140,8 +132,8 @@ public function getValidTests(): array
                     "prop":{"type":"string"}
                   }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{
                   "prop":"1",
                   "additionalProp":"2"
@@ -153,8 +145,8 @@ public function getValidTests(): array
                   },
                   "additionalProperties": {"type":"string"}
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{
                   "prop":"1",
                   "additionalProp":[]
@@ -166,8 +158,8 @@ public function getValidTests(): array
                   },
                   "additionalProperties": true
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{
                   "prop1": "a",
                   "prop2": "b"
@@ -178,8 +170,8 @@ public function getValidTests(): array
                     "type": "string"
                   }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{
                   "prop1": "a",
                   "prop2": "b"
@@ -188,8 +180,8 @@ public function getValidTests(): array
                   "type": "object",
                   "additionalProperties": true
                 }'
-            ],
-            'additional property casted into int when actually is numeric string (#784)' => [
+        ];
+        yield 'additional property casted into int when actually is numeric string (#784)' => [
                 '{
                     "prop1": {
                         "123": "a"
@@ -206,7 +198,6 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
-        ];
+            ];
     }
 }
diff --git a/tests/Constraints/ArraysTest.php b/tests/Constraints/ArraysTest.php
index aac3fc7f..4476c4ab 100644
--- a/tests/Constraints/ArraysTest.php
+++ b/tests/Constraints/ArraysTest.php
@@ -1,22 +1,17 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class ArraysTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
+        yield [
                 '{
                   "array":[1,2,"a"]
                 }',
@@ -29,8 +24,8 @@ public function getInvalidTests(): array
                     }
                   }
                 }'
-            ],
-            [
+            ];
+        yield [
                 '{
                   "array":[1,2,"a"]
                 }',
@@ -44,8 +39,8 @@ public function getInvalidTests(): array
                     }
                   }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{
                   "array":[1,2,null]
                 }',
@@ -58,8 +53,8 @@ public function getInvalidTests(): array
                     }
                   }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{"data": [1, 2, 3, "foo"]}',
                 '{
                     "type": "object",
@@ -71,8 +66,8 @@ public function getInvalidTests(): array
                         }
                     }
                 }'
-            ],
-            [ // Test array items.enum where type string fail validation if value(s) is/are not in items.enum
+        ];
+        yield 'Test array items.enum where type string fail validation if value(s) is/are not in items.enum' => [
                 '{"data": ["a", "b"]}',
                 '{
                     "type": "object",
@@ -86,8 +81,8 @@ public function getInvalidTests(): array
                         }
                     }
                 }'
-            ],
-            [ // Test array items.enum where type integer fail validation if value(s) is/are not in items.enum
+        ];
+        yield 'Test array items.enum where type integer fail validation if value(s) is/are not in items.enum' => [
                 '{"data": [1, 2]}',
                 '{
                     "type": "object",
@@ -101,8 +96,8 @@ public function getInvalidTests(): array
                         }
                     }
                 }'
-            ],
-            [ // Test array items.enum where type number fail validation if value(s) is/are not in items.enum
+        ];
+        yield 'Test array items.enum where type number fail validation if value(s) is/are not in items.enum' => [
                 '{"data": [1.25, 2.25]}',
                 '{
                     "type": "object",
@@ -116,8 +111,8 @@ public function getInvalidTests(): array
                         }
                     }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{"data": [{"not_a_string_but_object":"string_but_in_object"}]}',
                 '{
                     "type": "object",
@@ -129,14 +124,12 @@ public function getInvalidTests(): array
                         }
                     }
                 }'
-            ]
-        ];
+            ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
+        yield [
                 '{
                   "array":[1,2,"a"]
                 }',
@@ -146,8 +139,8 @@ public function getValidTests(): array
                     "array":{"type":"array"}
                   }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{
                   "array":[1,2,"a"]
                 }',
@@ -161,8 +154,8 @@ public function getValidTests(): array
                     }
                   }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{"data": [1, 2, 3, 4]}',
                 '{
                     "type": "object",
@@ -174,8 +167,8 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{"data": [1, "foo", false]}',
                 '{
                     "type": "object",
@@ -186,8 +179,8 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{"data": [1, "foo", false]}',
                 '{
                     "type": "object",
@@ -198,8 +191,8 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
-            [
+        ];
+        yield [
                 '{"data": [1, 2, 3, 4, 5]}',
                 '{
                     "type": "object",
@@ -210,8 +203,8 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
-            [ // test more schema items than array items
+        ];
+        yield 'test more schema items than array items' => [
                 '{"data": [1, 2]}',
                 '{
                     "type": "object",
@@ -226,8 +219,8 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
-            [ // Test array items.enum where type string passes validation if value(s) is/are in items.enum
+        ];
+        yield 'Test array items.enum where type string passes validation if value(s) is/are in items.enum' => [
                 '{"data": ["c", "c", "b"]}',
                 '{
                     "type": "object",
@@ -241,8 +234,8 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
-            [ // Test array items.enum where type integer passes validation if value(s) is/are in items.enum
+        ];
+        yield 'Test array items.enum where type integer passes validation if value(s) is/are in items.enum' => [
                 '{"data": [1, 1, 2]}',
                 '{
                     "type": "object",
@@ -256,8 +249,8 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
-            [ // Test array items.enum where type number passes validation if value(s) is/are in items.enum
+        ];
+        yield 'Test array items.enum where type number passes validation if value(s) is/are in items.enum' => [
                 '{"data": [1.25, 1.25, 2.25]}',
                 '{
                     "type": "object",
@@ -271,7 +264,6 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ],
         ];
     }
 }
diff --git a/tests/Constraints/BaseTestCase.php b/tests/Constraints/BaseTestCase.php
index 84daaf13..f65037d6 100644
--- a/tests/Constraints/BaseTestCase.php
+++ b/tests/Constraints/BaseTestCase.php
@@ -1,23 +1,16 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
+use Generator;
 use JsonSchema\Constraints\Constraint;
 use JsonSchema\Constraints\Factory;
 use JsonSchema\SchemaStorage;
 use JsonSchema\Uri\UriResolver;
 use JsonSchema\Validator;
 
-/**
- * @package JsonSchema\Tests\Constraints
- */
 abstract class BaseTestCase extends VeryBaseTestCase
 {
     protected $schemaSpec = 'http://json-schema.org/draft-04/schema#';
@@ -59,7 +52,7 @@ public function testInvalidCases(string $input, string $schema, ?int $checkMode
      */
     public function testInvalidCasesUsingAssoc($input, $schema, $checkMode = Constraint::CHECK_MODE_TYPE_CAST, $errors = []): void
     {
-        $checkMode = $checkMode === null ? Constraint::CHECK_MODE_TYPE_CAST : $checkMode;
+        $checkMode = $checkMode ?? Constraint::CHECK_MODE_TYPE_CAST;
         if ($this->validateSchema) {
             $checkMode |= Constraint::CHECK_MODE_VALIDATE_SCHEMA;
         }
@@ -94,14 +87,14 @@ public function testValidCases($input, $schema, $checkMode = Constraint::CHECK_M
         if ($this->validateSchema) {
             $checkMode |= Constraint::CHECK_MODE_VALIDATE_SCHEMA;
         }
-        $schemaStorage = new SchemaStorage($this->getUriRetrieverMock(json_decode($schema)));
+        $schemaStorage = new SchemaStorage($this->getUriRetrieverMock(json_decode($schema, false)));
         $schema = $schemaStorage->getSchema('http://www.my-domain.com/schema.json');
         if (is_object($schema) && !isset($schema->{'$schema'})) {
             $schema->{'$schema'} = $this->schemaSpec;
         }
 
         $validator = new Validator(new Factory($schemaStorage, null, $checkMode));
-        $checkValue = json_decode($input);
+        $checkValue = json_decode($input, false);
         $errorMask = $validator->validate($checkValue, $schema);
         $this->assertEquals(0, $errorMask);
 
@@ -135,17 +128,17 @@ public function testValidCasesUsingAssoc($input, $schema, $checkMode = Constrain
         $this->assertTrue($validator->isValid(), print_r($validator->getErrors(), true));
     }
 
-    abstract public function getValidTests(): array;
+    abstract public function getValidTests(): Generator;
 
-    public function getValidForAssocTests(): array
+    public function getValidForAssocTests(): Generator
     {
-        return $this->getValidTests();
+        yield from $this->getValidTests();
     }
 
-    abstract public function getInvalidTests(): array;
+    abstract public function getInvalidTests(): Generator;
 
-    public function getInvalidForAssocTests(): array
+    public function getInvalidForAssocTests(): Generator
     {
-        return $this->getInvalidTests();
+        yield from $this->getInvalidTests();
     }
 }
diff --git a/tests/Constraints/BasicTypesTest.php b/tests/Constraints/BasicTypesTest.php
index 01e1f7ba..497cb578 100644
--- a/tests/Constraints/BasicTypesTest.php
+++ b/tests/Constraints/BasicTypesTest.php
@@ -1,150 +1,143 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class BasicTypesTest extends BaseTestCase
 {
+    /** @var string */
     protected $schemaSpec = 'http://json-schema.org/draft-03/schema#';
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "string":null
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "string":{"type":"string"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{
-                  "number":null
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "number":{"type":"number"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{
-                  "integer":null
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "integer":{"type":"integer"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{
-                  "boolean":null
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "boolean":{"type":"boolean"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{
-                  "object":null
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "object":{"type":"object"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{
-                  "array":null
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "array":{"type":"array"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{
-                  "null":1
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "null":{"type":"null"}
-                  },
-                  "additionalProperties":false
-                }'
-            ]
+        yield [
+            '{
+              "string":null
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "string":{"type":"string"}
+              },
+              "additionalProperties":false
+            }'
         ];
+        yield [
+            '{
+              "number":null
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "number":{"type":"number"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{
+              "integer":null
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "integer":{"type":"integer"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{
+              "boolean":null
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "boolean":{"type":"boolean"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{
+              "object":null
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "object":{"type":"object"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{
+              "array":null
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "array":{"type":"array"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{
+              "null":1
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "null":{"type":"null"}
+              },
+              "additionalProperties":false
+            }'
+            ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "string":"string test",
-                  "number":1,
-                  "integer":1,
-                  "boolean":true,
-                  "object":{},
-                  "array":[],
-                  "null":null,
-                  "any": "string",
-                  "any1": 2.6,
-                  "any2": 4,
-                  "any3": false,
-                  "any4": {},
-                  "any5": [],
-                  "any6": null
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "string":{"type":"string"},
-                    "number":{"type":"number"},
-                    "integer":{"type":"integer"},
-                    "boolean":{"type":"boolean"},
-                    "object":{"type":"object"},
-                    "array":{"type":"array"},
-                    "null":{"type":"null"},
-                    "any": {"type":"any"},
-                    "any1": {"type":"any"},
-                    "any2": {"type":"any"},
-                    "any3": {"type":"any"},
-                    "any4": {"type":"any"},
-                    "any5": {"type":"any"},
-                    "any6": {"type":"any"}
-                  },
-                  "additionalProperties":false
-                }'
-            ]
+        yield [
+            '{
+              "string":"string test",
+              "number":1,
+              "integer":1,
+              "boolean":true,
+              "object":{},
+              "array":[],
+              "null":null,
+              "any": "string",
+              "any1": 2.6,
+              "any2": 4,
+              "any3": false,
+              "any4": {},
+              "any5": [],
+              "any6": null
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "string":{"type":"string"},
+                "number":{"type":"number"},
+                "integer":{"type":"integer"},
+                "boolean":{"type":"boolean"},
+                "object":{"type":"object"},
+                "array":{"type":"array"},
+                "null":{"type":"null"},
+                "any": {"type":"any"},
+                "any1": {"type":"any"},
+                "any2": {"type":"any"},
+                "any3": {"type":"any"},
+                "any4": {"type":"any"},
+                "any5": {"type":"any"},
+                "any6": {"type":"any"}
+              },
+              "additionalProperties":false
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/CoerciveTest.php b/tests/Constraints/CoerciveTest.php
index 3c028ba0..47dcc072 100644
--- a/tests/Constraints/CoerciveTest.php
+++ b/tests/Constraints/CoerciveTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
diff --git a/tests/Constraints/ConstTest.php b/tests/Constraints/ConstTest.php
index ec4f688d..25235f0c 100644
--- a/tests/Constraints/ConstTest.php
+++ b/tests/Constraints/ConstTest.php
@@ -1,53 +1,49 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class ConstTest extends BaseTestCase
 {
+    /** @var string */
     protected $schemaSpec = 'http://json-schema.org/draft-06/schema#';
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            'Object with inner string value' => [
-                '{"value":"foo"}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","const":"bar"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            'Object with inner integer value' => [
-                '{"value":5}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"integer","const":6}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            'Object with inner boolean value' => [
-                '{"value":false}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"boolean","const":true}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            'Object with inner numerical string value' => [
+        yield 'Object with inner string value' => [
+            '{"value":"foo"}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","const":"bar"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield 'Object with inner integer value' => [
+            '{"value":5}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"integer","const":6}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield 'Object with inner boolean value' => [
+            '{"value":false}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"boolean","const":true}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield 'Object with inner numerical string value' => [
                 '{
                     "value": {
                         "foo": "12"
@@ -64,54 +60,52 @@ public function getInvalidTests(): array
                         }
                     }
                 }'
-            ]
-        ];
+            ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            'String value' => [
-                '{"value":"bar"}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","const":"bar"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            'Boolean(false) value' => [
-                '{"value":false}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"boolean","const":false}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            'Boolean(true) value' => [
-                '{"value":true}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"boolean","const":true}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            'Integer value' => [
-                '{"value":5}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"integer","const":5}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            'Object with inner integer value' => [
+        yield 'String value' => [
+            '{"value":"bar"}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","const":"bar"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield 'Boolean(false) value' => [
+            '{"value":false}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"boolean","const":false}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield 'Boolean(true) value' => [
+            '{"value":true}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"boolean","const":true}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield 'Integer value' => [
+            '{"value":5}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"integer","const":5}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield 'Object with inner integer value' => [
                 '{
                     "value": {
                         "foo": 12
@@ -128,7 +122,6 @@ public function getValidTests(): array
                         }
                     }
                 }'
-            ]
-        ];
+            ];
     }
 }
diff --git a/tests/Constraints/DefaultPropertiesTest.php b/tests/Constraints/DefaultPropertiesTest.php
index 28498352..e43b980e 100644
--- a/tests/Constraints/DefaultPropertiesTest.php
+++ b/tests/Constraints/DefaultPropertiesTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
diff --git a/tests/Constraints/DependenciesTest.php b/tests/Constraints/DependenciesTest.php
index ff3ffb8e..ca0dc63a 100644
--- a/tests/Constraints/DependenciesTest.php
+++ b/tests/Constraints/DependenciesTest.php
@@ -1,151 +1,144 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class DependenciesTest extends BaseTestCase
 {
+    /** @var string */
     protected $schemaSpec = 'http://json-schema.org/draft-03/schema#';
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{"bar": 1}',
-                '{
-                    "dependencies": {"bar": "foo"}
-                }'
-            ],
-            [
-                '{"bar": 1}',
-                '{
-                    "dependencies": {"bar": ["foo"]}
-                }'
-            ],
-            [
-                '{"bar": 1, "foo": 1}',
-                '{
-                    "dependencies": {"bar": ["foo", "baz"]}
-                }'
-            ],
-            [
-                '{"bar": 1, "foo": 1}',
-                '{
-                    "dependencies": {"bar": {
-                        "properties": {
-                            "foo": {"type": "string"}
-                        }
-                    }}
-                }'
-            ],
-            [
-                '{"bar": 1}',
-                '{
-                    "dependencies": {"bar": {
-                        "properties": {
-                            "foo": {"type": "integer", "required": true}
-                        }
-                    }}
-                }'
-            ],
-            [
-                '{"bar": 1}',
-                '{
-                    "dependencies": {"bar": {
-                        "properties": {
-                            "foo": {"type": "integer"}
-                        },
-                        "required": ["foo"]
-                    }}
-                }'
-            ],
-            [
-                '{"bar": true, "foo": "ick"}',
-                '{
-                    "dependencies": {"bar": {
-                        "properties": {
-                            "bar": {"type": "integer"},
-                            "foo": {"type": "integer"}
-                        }
-                    }}
-                }'
-            ]
+        yield [
+            '{"bar": 1}',
+            '{
+                "dependencies": {"bar": "foo"}
+            }'
+        ];
+        yield [
+            '{"bar": 1}',
+            '{
+                "dependencies": {"bar": ["foo"]}
+            }'
+        ];
+        yield [
+            '{"bar": 1, "foo": 1}',
+            '{
+                "dependencies": {"bar": ["foo", "baz"]}
+            }'
+        ];
+        yield [
+            '{"bar": 1, "foo": 1}',
+            '{
+                "dependencies": {"bar": {
+                    "properties": {
+                        "foo": {"type": "string"}
+                    }
+                }}
+            }'
+        ];
+        yield [
+            '{"bar": 1}',
+            '{
+                "dependencies": {"bar": {
+                    "properties": {
+                        "foo": {"type": "integer", "required": true}
+                    }
+                }}
+            }'
+        ];
+        yield [
+            '{"bar": 1}',
+            '{
+                "dependencies": {"bar": {
+                    "properties": {
+                        "foo": {"type": "integer"}
+                    },
+                    "required": ["foo"]
+                }}
+            }'
+        ];
+        yield [
+            '{"bar": true, "foo": "ick"}',
+            '{
+                "dependencies": {"bar": {
+                    "properties": {
+                        "bar": {"type": "integer"},
+                        "foo": {"type": "integer"}
+                    }
+                }}
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{}',
-                '{
-                    "dependencies": {"bar": "foo"}
-                }'
-            ],
-            [
-                '{"foo": 1}',
-                '{
-                    "dependencies": {"bar": "foo"}
-                }'
-            ],
-            [
-                '"foo"',
-                '{
-                    "dependencies": {"bar": "foo"}
-                }'
-            ],
-            [
-                '{"bar": 1, "foo": 1}',
-                '{
-                    "dependencies": {"bar": "foo"}
-                }'
-            ],
-            [
-                '{"bar": 1, "foo": 1, "baz": 1}',
-                '{
-                    "dependencies": {"bar": ["foo", "baz"]}
-                }'
-            ],
-            [
-                '{}',
-                '{
-                    "dependencies": {"bar": ["foo", "baz"]}
-                }'
-            ],
-            [
-                '{"foo": 1, "baz": 1}',
-                '{
-                    "dependencies": {"bar": ["foo", "baz"]}
-                }'
-            ],
-            [
-                '{"bar": 1}',
-                '{
-                    "dependencies": {"bar": {
-                        "properties": {
-                            "foo": {"type": "integer"}
-                        }
-                    }}
-                }'
-            ],
-            [
-                '{"bar": 1, "foo": 1}',
-                '{
-                    "dependencies": {"bar": {
-                        "properties": {
-                            "bar": {"type": "integer"},
-                            "foo": {"type": "integer"}
-                        }
-                    }}
-                }'
-            ]
+        yield [
+            '{}',
+            '{
+                "dependencies": {"bar": "foo"}
+            }'
+        ];
+        yield [
+            '{"foo": 1}',
+            '{
+                "dependencies": {"bar": "foo"}
+            }'
+        ];
+        yield [
+            '"foo"',
+            '{
+                "dependencies": {"bar": "foo"}
+            }'
+        ];
+        yield [
+            '{"bar": 1, "foo": 1}',
+            '{
+                "dependencies": {"bar": "foo"}
+            }'
+        ];
+        yield [
+            '{"bar": 1, "foo": 1, "baz": 1}',
+            '{
+                "dependencies": {"bar": ["foo", "baz"]}
+            }'
+        ];
+        yield [
+            '{}',
+            '{
+                "dependencies": {"bar": ["foo", "baz"]}
+            }'
+        ];
+        yield [
+            '{"foo": 1, "baz": 1}',
+            '{
+                "dependencies": {"bar": ["foo", "baz"]}
+            }'
+        ];
+        yield [
+            '{"bar": 1}',
+            '{
+                "dependencies": {"bar": {
+                    "properties": {
+                        "foo": {"type": "integer"}
+                    }
+                }}
+            }'
+        ];
+        yield [
+            '{"bar": 1, "foo": 1}',
+            '{
+                "dependencies": {"bar": {
+                    "properties": {
+                        "bar": {"type": "integer"},
+                        "foo": {"type": "integer"}
+                    }
+                }}
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/DisallowTest.php b/tests/Constraints/DisallowTest.php
index 1fe93f6c..943c94aa 100644
--- a/tests/Constraints/DisallowTest.php
+++ b/tests/Constraints/DisallowTest.php
@@ -1,170 +1,163 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
+/**
+ * Schemas in these tests look like draft-03, but the 'disallow' patterns provided are in
+ * violation of the spec - 'disallow' as defined in draft-03 accepts the same values as the
+ * 'type' option, and cannot take arbitrary patterns. The implementation in this library is
+ * probably deliberate, but noting that it's invalid, schema validation has been disabled
+ * for these tests. The 'disallow' option was removed permanently in draft-04.
+ */
 class DisallowTest extends BaseTestCase
 {
-    // schemas in these tests look like draft-03, but the 'disallow' patterns provided are in
-    // violation of the spec - 'disallow' as defined in draft-03 accepts the same values as the
-    // 'type' option, and cannot take arbitrary patterns. The implementation in this library is
-    // probably deliberate, but noting that it's invalid, schema validation has been disabled
-    // for these tests. The 'disallow' option was removed permanently in draft-04.
+    /** @var string */
     protected $schemaSpec = 'http://json-schema.org/draft-03/schema#';
-    protected $validateSchema = false;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"The xpto is weird"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{
-                      "type":"any",
-                      "disallow":{"type":"string","pattern":"xpto"}
-                    }
-                  }
-                }'
-            ],
-            [
-                '{
-                  "value":null
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{
-                      "type":"any",
-                      "disallow":{"type":"null"}
-                    }
-                  }
-                }'
-            ],
-            [
-                '{"value": 1}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "any", "disallow": "integer"}
-                    }
-                }'
-            ],
-            [
-                '{"value": true}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "any", "disallow": ["integer", "boolean"]}
-                    }
-                }'
-            ],
-            [
-                '{"value": "foo"}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {
-                            "type": "any",
-                            "disallow":
-                                ["string", {
-                                    "type": "object",
-                                    "properties": {
-                                        "foo": {"type": "string"}
-                                    }
-                                }]
-                        }
+        yield [
+            '{
+              "value":"The xpto is weird"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{
+                  "type":"any",
+                  "disallow":{"type":"string","pattern":"xpto"}
+                }
+              }
+            }'
+        ];
+        yield [
+            '{
+              "value":null
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{
+                  "type":"any",
+                  "disallow":{"type":"null"}
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"value": 1}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "any", "disallow": "integer"}
+                }
+            }'
+        ];
+        yield [
+            '{"value": true}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "any", "disallow": ["integer", "boolean"]}
+                }
+            }'
+        ];
+        yield [
+            '{"value": "foo"}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {
+                        "type": "any",
+                        "disallow":
+                            ["string", {
+                                "type": "object",
+                                "properties": {
+                                    "foo": {"type": "string"}
+                                }
+                            }]
                     }
-                }'
-            ],
-            [
-                '{"value": {"foo": "bar"}}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {
-                            "type": "any",
-                            "disallow":
-                                ["string", {
-                                    "type": "object",
-                                    "properties": {
-                                        "foo": {"type": "string"}
-                                    }
-                                }]
-                        }
+                }
+            }'
+        ];
+        yield [
+            '{"value": {"foo": "bar"}}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {
+                        "type": "any",
+                        "disallow":
+                            ["string", {
+                                "type": "object",
+                                "properties": {
+                                    "foo": {"type": "string"}
+                                }
+                            }]
                     }
-                }'
-            ]
+                }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"The xpto is weird"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{
-                      "type":"any",
-                      "disallow":{"type":"string","pattern":"^xpto"}
-                    }
-                  }
-                }'
-            ],
-            [
-                '{
-                  "value":1
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{
-                      "type":"any",
-                      "disallow":{"type":"null"}
-                    }
-                  }
-                }'
-            ],
-            [
-                '{"value": {"foo": 1}}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {
-                            "type": "any",
-                            "disallow":
-                                ["string", {
-                                    "type": "object",
-                                    "properties": {
-                                        "foo": {"type": "string"}
-                                    }
-                                }]
-                        }
-                    }
-                }'
-            ],
-            [
-                '{"value": true}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "any", "disallow": "string"}
+        yield [
+            '{
+              "value":"The xpto is weird"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{
+                  "type":"any",
+                  "disallow":{"type":"string","pattern":"^xpto"}
+                }
+              }
+            }'
+        ];
+        yield [
+            '{
+              "value":1
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{
+                  "type":"any",
+                  "disallow":{"type":"null"}
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"value": {"foo": 1}}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {
+                        "type": "any",
+                        "disallow":
+                            ["string", {
+                                "type": "object",
+                                "properties": {
+                                    "foo": {"type": "string"}
+                                }
+                            }]
                     }
-                }'
-            ]
+                }
+            }'
+        ];
+        yield [
+            '{"value": true}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "any", "disallow": "string"}
+                }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/DivisibleByTest.php b/tests/Constraints/DivisibleByTest.php
index 354d6a29..23506d77 100644
--- a/tests/Constraints/DivisibleByTest.php
+++ b/tests/Constraints/DivisibleByTest.php
@@ -1,97 +1,89 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class DivisibleByTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{"value": 5.6333}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"number","divisibleBy":3}
-                  }
-                }'
-            ],
-            [
-                '{"value": 35}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "divisibleBy": 1.5}
-                    }
-                }'
-            ],
-            [
-                '{"value": 0.00751}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "number", "divisibleBy": 0.0001}
-                    }
-                }'
-            ],
-            [
-                '{"value": 7}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "divisibleBy": 2}
-                    }
-                }'
-            ]
+        yield [
+            '{"value": 5.6333}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"number","divisibleBy":3}
+              }
+            }'
+        ];
+        yield [
+            '{"value": 35}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "divisibleBy": 1.5}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 0.00751}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "number", "divisibleBy": 0.0001}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 7}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "divisibleBy": 2}
+                }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{"value": 6}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"number","divisibleBy":3}
-                  }
-                }'
-            ],
-            [
-                '{"value": 4.5}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "number", "divisibleBy": 1.5}
-                    }
-                }'
-            ],
-            [
-                '{"value": 0.0075}',
-                '{
-                    "properties": {
-                        "value": {"type": "number", "divisibleBy": 0.0001}
-                    }
-                }'
-            ],
-            [
-                '{"value": 1}',
-                '{
-                    "properties": {
-                        "value": {"type": "number", "divisibleBy": 0.02}
-                    }
-                }'
-            ]
+        yield [
+            '{"value": 6}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"number","divisibleBy":3}
+              }
+            }'
+        ];
+        yield [
+            '{"value": 4.5}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "number", "divisibleBy": 1.5}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 0.0075}',
+            '{
+                "properties": {
+                    "value": {"type": "number", "divisibleBy": 0.0001}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 1}',
+            '{
+                "properties": {
+                    "value": {"type": "number", "divisibleBy": 0.02}
+                }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/EnumTest.php b/tests/Constraints/EnumTest.php
index a70f871f..69f1de10 100644
--- a/tests/Constraints/EnumTest.php
+++ b/tests/Constraints/EnumTest.php
@@ -1,198 +1,191 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class EnumTest extends BaseTestCase
 {
+    /** @var string */
     protected $schemaSpec = 'http://json-schema.org/draft-03/schema#';
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"Morango"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","enum":["Abacate","Manga","Pitanga"]}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{
-                      "type":"string",
-                      "enum":["Abacate","Manga","Pitanga"],
-                      "required":true
+        yield [
+            '{
+              "value":"Morango"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","enum":["Abacate","Manga","Pitanga"]}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{
+                  "type":"string",
+                  "enum":["Abacate","Manga","Pitanga"],
+                  "required":true
+                }
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{"value": "4"}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {
+                        "type": "integer", "enum": [1, 2, 3]
                     }
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{"value": "4"}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {
-                            "type": "integer", "enum": [1, 2, 3]
-                        }
-                    },
-                    "additionalProperties": false
-                }'
-            ],
-            [
-                '{"value": {"foo": false}}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {
-                            "type": "any", "enum": [6, "foo", [], true, {"foo": 12}]
-                        }
-                    },
-                    "additionalProperties": false
-                }'
-            ],
-            [
-                '{
+                },
+                "additionalProperties": false
+            }'
+        ];
+        yield [
+            '{"value": {"foo": false}}',
+            '{
+                "type": "object",
+                "properties": {
                     "value": {
-                        "foo": "12"
+                        "type": "any", "enum": [6, "foo", [], true, {"foo": 12}]
                     }
-                }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {
-                            "type": "any", 
-                            "enum": [
-                                6, 
-                                "foo", 
-                                [], 
-                                true, 
-                                {
-                                    "foo": 12
-                                }
-                            ]
-                        }
+                },
+                "additionalProperties": false
+            }'
+        ];
+        yield [
+            '{
+                "value": {
+                    "foo": "12"
+                }
+            }',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {
+                        "type": "any", 
+                        "enum": [
+                            6, 
+                            "foo", 
+                            [], 
+                            true, 
+                            {
+                                "foo": 12
+                            }
+                        ]
                     }
-                }'
-            ]
+                }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"Abacate"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","enum":["Abacate","Manga","Pitanga"]}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","enum":["Abacate","Manga","Pitanga"]}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{
-                      "type":"string",
-                      "enum":["Abacate","Manga","Pitanga"],
-                      "required":false
-                    }
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{"value": 1}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "enum": [1, 2, 3]}
-                    }
-                }'
-            ],
-            [
-                '{"value": []}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "any", "enum": [6, "foo", [], true, {"foo": 12}]}
-                    },
-                    "additionalProperties": false
-                }'
-            ],
-            [
-                '{
+        yield [
+            '{
+              "value":"Abacate"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","enum":["Abacate","Manga","Pitanga"]}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","enum":["Abacate","Manga","Pitanga"]}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{}',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{
+                  "type":"string",
+                  "enum":["Abacate","Manga","Pitanga"],
+                  "required":false
+                }
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{"value": 1}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "enum": [1, 2, 3]}
+                }
+            }'
+        ];
+        yield [
+            '{"value": []}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "any", "enum": [6, "foo", [], true, {"foo": 12}]}
+                },
+                "additionalProperties": false
+            }'
+        ];
+        yield [
+            '{
+                "value": {
+                    "foo": 12
+                }
+            }',
+            '{
+                "type": "object",
+                "properties": {
                     "value": {
-                        "foo": 12
-                    }
-                }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {
-                            "type": "any",
-                            "enum": [
-                                6,
-                                "foo",
-                                [],
-                                true,
-                                {
-                                    "foo": 12
-                                }
-                            ]
-                        }
+                        "type": "any",
+                        "enum": [
+                            6,
+                            "foo",
+                            [],
+                            true,
+                            {
+                                "foo": 12
+                            }
+                        ]
                     }
-                }'
-            ],
-            'Number values with mathematical equality are considered valid' => [
-                'data' => '12',
-                'schema' => '{
-                    "type": "any",
-                    "enum": [
-                        12.0
-                    ]
-                }'
-            ],
-            'Array with number values with mathematical equality are considered valid' => [
-                'input' => '[ 0.0 ]',
-                'schema' => '{
-                    "enum": [
-                        [ 0 ]
-                    ]
-                }',
-            ]
+                }
+            }'
+        ];
+        yield 'Number values with mathematical equality are considered valid' => [
+            'data' => '12',
+            'schema' => '{
+                "type": "any",
+                "enum": [
+                    12.0
+                ]
+            }'
+        ];
+        yield 'Array with number values with mathematical equality are considered valid' => [
+            'input' => '[ 0.0 ]',
+            'schema' => '{
+                "enum": [
+                    [ 0 ]
+                ]
+            }',
         ];
     }
 }
diff --git a/tests/Constraints/ExtendsTest.php b/tests/Constraints/ExtendsTest.php
index 286b24b8..2fd0adc1 100644
--- a/tests/Constraints/ExtendsTest.php
+++ b/tests/Constraints/ExtendsTest.php
@@ -1,154 +1,147 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class ExtendsTest extends BaseTestCase
 {
+    /** @var string */
     protected $schemaSpec = 'http://json-schema.org/draft-03/schema#';
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "name":"bruno",
-                  "age":50
-                }',
-                '{
+        yield [
+            '{
+              "name":"bruno",
+              "age":50
+            }',
+            '{
+                "properties": {
+                    "name": {"type": "string"},
+                    "age": {
+                        "type": "integer",
+                        "maximum": 120
+                    }
+                },
+                "extends": {
                     "properties": {
-                        "name": {"type": "string"},
-                        "age": {
-                            "type": "integer",
-                            "maximum": 120
-                        }
-                    },
-                    "extends": {
-                        "properties": {
-                            "age": {"minimum": 70}
-                        }
+                        "age": {"minimum": 70}
+                    }
+                }
+            }'
+        ];
+        yield [
+            '{
+              "name":"bruno",
+              "age":180
+            }',
+            '{
+                "properties": {
+                    "name": {"type": "string"},
+                    "age": {
+                        "type": "integer",
+                        "maximum": 120
                     }
-                }'
-            ],
-            [
-                '{
-                  "name":"bruno",
-                  "age":180
-                }',
-                '{
+                },
+                "extends": {
                     "properties": {
-                        "name": {"type": "string"},
-                        "age": {
-                            "type": "integer",
-                            "maximum": 120
-                        }
-                    },
-                    "extends": {
-                        "properties": {
-                            "age": {"minimum":70}
-                        }
+                        "age": {"minimum":70}
                     }
-                }'
-            ],
-            [
-                '{"foo": 2, "bar": "baz"}',
-                '{
+                }
+            }'
+        ];
+        yield [
+            '{"foo": 2, "bar": "baz"}',
+            '{
+                "properties": {
+                    "bar": {"type": "integer", "required": true}
+                },
+                "extends": {
                     "properties": {
-                        "bar": {"type": "integer", "required": true}
-                    },
-                    "extends": {
+                        "foo": {"type": "string", "required": true}
+                    }
+                }
+            }'
+        ];
+        yield [
+            '{"bar": 2}',
+            '{
+                "properties": {
+                    "bar": {"type": "integer", "required": true}
+                },
+                "extends" : [
+                    {
                         "properties": {
                             "foo": {"type": "string", "required": true}
                         }
-                    }
-                }'
-            ],
-            [
-                '{"bar": 2}',
-                '{
-                    "properties": {
-                        "bar": {"type": "integer", "required": true}
                     },
-                    "extends" : [
-                        {
-                            "properties": {
-                                "foo": {"type": "string", "required": true}
-                            }
-                        },
-                        {
-                            "properties": {
-                                "baz": {"type": "null", "required": true}
-                            }
+                    {
+                        "properties": {
+                            "baz": {"type": "null", "required": true}
                         }
-                    ]
-                }'
-            ]
+                    }
+                ]
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "name":"bruno",
-                  "age":80
-                }',
-                '{
+        yield [
+            '{
+              "name":"bruno",
+              "age":80
+            }',
+            '{
+                "properties": {
+                    "name": {"type": "string"},
+                    "age": {
+                        "type": "integer",
+                        "maximum": 120
+                    }
+                },
+                "extends": {
                     "properties": {
-                        "name": {"type": "string"},
-                        "age": {
-                            "type": "integer",
-                            "maximum": 120
-                        }
-                    },
-                    "extends": {
-                        "properties": {
-                            "age": {"minimum": 70}
-                        }
+                        "age": {"minimum": 70}
                     }
-                }'
-            ],
-            [
-                '{"foo": "baz", "bar": 2}',
-                '{
+                }
+            }'
+        ];
+        yield [
+            '{"foo": "baz", "bar": 2}',
+            '{
+                "properties": {
+                    "bar": {"type": "integer", "required": true}
+                },
+                "extends": {
                     "properties": {
-                        "bar": {"type": "integer", "required": true}
-                    },
-                    "extends": {
+                        "foo": {"type": "string", "required": true}
+                    }
+                }
+            }'
+        ];
+        yield [
+            '{"foo": "ick", "bar": 2, "baz": null}',
+            '{
+                "properties": {
+                    "bar": {"type": "integer", "required": true}
+                },
+                "extends" : [
+                    {
                         "properties": {
                             "foo": {"type": "string", "required": true}
                         }
-                    }
-                }'
-            ],
-            [
-                '{"foo": "ick", "bar": 2, "baz": null}',
-                '{
-                    "properties": {
-                        "bar": {"type": "integer", "required": true}
                     },
-                    "extends" : [
-                        {
-                            "properties": {
-                                "foo": {"type": "string", "required": true}
-                            }
-                        },
-                        {
-                            "properties": {
-                                "baz": {"type": "null", "required": true}
-                            }
+                    {
+                        "properties": {
+                            "baz": {"type": "null", "required": true}
                         }
-                    ]
-                }'
-            ]
+                    }
+                ]
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/FactoryTest.php b/tests/Constraints/FactoryTest.php
index 9136f50d..0ff6e922 100644
--- a/tests/Constraints/FactoryTest.php
+++ b/tests/Constraints/FactoryTest.php
@@ -1,12 +1,5 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
 declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
diff --git a/tests/Constraints/FormatTest.php b/tests/Constraints/FormatTest.php
index 25eab1c0..72471054 100644
--- a/tests/Constraints/FormatTest.php
+++ b/tests/Constraints/FormatTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -15,6 +10,7 @@
 
 class FormatTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
     public function setUp(): void
@@ -95,204 +91,197 @@ public function testDisabledFormat($string, $format): void
         $this->assertEmpty($validator->getErrors());
     }
 
-    public function getValidFormats(): array
+    public function getValidFormats(): \Generator
     {
-        return [
-            ['2001-01-23', 'date'],
-            ['2000-02-29', 'date'],
-            [42, 'date'],
-            [4.2, 'date'],
-
-            ['12:22:01', 'time'],
-            ['00:00:00', 'time'],
-            ['23:59:59', 'time'],
-            [42, 'time'],
-            [4.2, 'time'],
-
-            ['2000-05-01T12:12:12Z', 'date-time'],
-            ['2000-05-01T12:12:12+0100', 'date-time'],
-            ['2000-05-01T12:12:12+01:00', 'date-time'],
-            ['2000-05-01T12:12:12.123456Z', 'date-time'],
-            ['2000-05-01T12:12:12.123Z', 'date-time'],
-            ['2000-05-01T12:12:12.123000Z', 'date-time'],
-            ['2000-05-01T12:12:12.0Z', 'date-time'],
-            ['2000-05-01T12:12:12.000Z', 'date-time'],
-            ['2000-05-01T12:12:12.000000Z', 'date-time'],
-            [42, 'date-time'],
-            [4.2, 'date-time'],
-
-            ['0', 'utc-millisec'],
-
-            ['aqua', 'color'],
-            ['black', 'color'],
-            ['blue', 'color'],
-            ['fuchsia', 'color'],
-            ['gray', 'color'],
-            ['green', 'color'],
-            ['lime', 'color'],
-            ['maroon', 'color'],
-            ['navy', 'color'],
-            ['olive', 'color'],
-            ['orange', 'color'],
-            ['purple', 'color'],
-            ['red', 'color'],
-            ['silver', 'color'],
-            ['teal', 'color'],
-            ['white', 'color'],
-            ['yellow', 'color'],
-            ['#fff', 'color'],
-            ['#00cc00', 'color'],
-            [42, 'color'],
-            [4.2, 'color'],
-
-            ['background: blue', 'style'],
-            ['color: #000;', 'style'],
-
-            ['555 320 1212', 'phone'],
-
-            ['http://bluebox.org', 'uri'],
-            ['//bluebox.org', 'uri-reference'],
-            ['/absolutePathReference/', 'uri-reference'],
-            ['./relativePathReference/', 'uri-reference'],
-            ['./relative:PathReference/', 'uri-reference'],
-            ['relativePathReference/', 'uri-reference'],
-            ['relative/Path:Reference/', 'uri-reference'],
-            [42, 'uri-reference'],
-            [4.2, 'uri-reference'],
-
-            ['info@something.edu', 'email'],
-            [42, 'email'],
-            [4.2, 'email'],
-
-            ['10.10.10.10', 'ip-address'],
-            ['127.0.0.1', 'ip-address'],
-            [42, 'ip-address'],
-            [4.2, 'ip-address'],
-
-            ['127.0.0.1', 'ipv4'],
-            [42, 'ipv4'],
-            [4.2, 'ipv4'],
-
-            ['::ff', 'ipv6'],
-            [42, 'ipv6'],
-            [4.2, 'ipv6'],
-
-            ['www.example.com', 'host-name'],
-            ['3v4l.org', 'host-name'],
-            ['a-valid-host.com', 'host-name'],
-            ['localhost', 'host-name'],
-            [42, 'host-name'],
-            [4.2, 'host-name'],
-
-            ['www.example.com', 'hostname'],
-            ['3v4l.org', 'hostname'],
-            ['a-valid-host.com', 'hostname'],
-            ['localhost', 'hostname'],
-            [42, 'hostname'],
-            [4.2, 'hostname'],
-
-            ['anything', '*'],
-            ['unknown', '*'],
-        ];
+        yield ['2001-01-23', 'date'];
+        yield ['2000-02-29', 'date'];
+        yield [42, 'date'];
+        yield [4.2, 'date'];
+
+        yield ['12:22:01', 'time'];
+        yield ['00:00:00', 'time'];
+        yield ['23:59:59', 'time'];
+        yield [42, 'time'];
+        yield [4.2, 'time'];
+
+        yield ['2000-05-01T12:12:12Z', 'date-time'];
+        yield ['2000-05-01T12:12:12+0100', 'date-time'];
+        yield ['2000-05-01T12:12:12+01:00', 'date-time'];
+        yield ['2000-05-01T12:12:12.123456Z', 'date-time'];
+        yield ['2000-05-01T12:12:12.123Z', 'date-time'];
+        yield ['2000-05-01T12:12:12.123000Z', 'date-time'];
+        yield ['2000-05-01T12:12:12.0Z', 'date-time'];
+        yield ['2000-05-01T12:12:12.000Z', 'date-time'];
+        yield ['2000-05-01T12:12:12.000000Z', 'date-time'];
+        yield [42, 'date-time'];
+        yield [4.2, 'date-time'];
+
+        yield ['0', 'utc-millisec'];
+
+        yield ['aqua', 'color'];
+        yield ['black', 'color'];
+        yield ['blue', 'color'];
+        yield ['fuchsia', 'color'];
+        yield ['gray', 'color'];
+        yield ['green', 'color'];
+        yield ['lime', 'color'];
+        yield ['maroon', 'color'];
+        yield ['navy', 'color'];
+        yield ['olive', 'color'];
+        yield ['orange', 'color'];
+        yield ['purple', 'color'];
+        yield ['red', 'color'];
+        yield ['silver', 'color'];
+        yield ['teal', 'color'];
+        yield ['white', 'color'];
+        yield ['yellow', 'color'];
+        yield ['#fff', 'color'];
+        yield ['#00cc00', 'color'];
+        yield [42, 'color'];
+        yield [4.2, 'color'];
+
+        yield ['background: blue', 'style'];
+        yield ['color: #000;', 'style'];
+
+        yield ['555 320 1212', 'phone'];
+
+        yield ['http://bluebox.org', 'uri'];
+        yield ['//bluebox.org', 'uri-reference'];
+        yield ['/absolutePathReference/', 'uri-reference'];
+        yield ['./relativePathReference/', 'uri-reference'];
+        yield ['./relative:PathReference/', 'uri-reference'];
+        yield ['relativePathReference/', 'uri-reference'];
+        yield ['relative/Path:Reference/', 'uri-reference'];
+        yield [42, 'uri-reference'];
+        yield [4.2, 'uri-reference'];
+
+        yield ['info@something.edu', 'email'];
+        yield [42, 'email'];
+        yield [4.2, 'email'];
+
+        yield ['10.10.10.10', 'ip-address'];
+        yield ['127.0.0.1', 'ip-address'];
+        yield [42, 'ip-address'];
+        yield [4.2, 'ip-address'];
+
+        yield ['127.0.0.1', 'ipv4'];
+        yield [42, 'ipv4'];
+        yield [4.2, 'ipv4'];
+
+        yield ['::ff', 'ipv6'];
+        yield [42, 'ipv6'];
+        yield [4.2, 'ipv6'];
+
+        yield ['www.example.com', 'host-name'];
+        yield ['3v4l.org', 'host-name'];
+        yield ['a-valid-host.com', 'host-name'];
+        yield ['localhost', 'host-name'];
+        yield [42, 'host-name'];
+        yield [4.2, 'host-name'];
+
+        yield ['www.example.com', 'hostname'];
+        yield ['3v4l.org', 'hostname'];
+        yield ['a-valid-host.com', 'hostname'];
+        yield ['localhost', 'hostname'];
+        yield [42, 'hostname'];
+        yield [4.2, 'hostname'];
+
+        yield ['anything', '*'];
+        yield ['unknown', '*'];
     }
 
-    public function getInvalidFormats(): array
+    public function getInvalidFormats(): \Generator
     {
-        return [
-            ['January 1st, 1910', 'date'],
-            ['199-01-1', 'date'],
-            ['2012-0-11', 'date'],
-            ['2012-10-1', 'date'],
+        yield ['January 1st, 1910', 'date'];
+        yield ['199-01-1', 'date'];
+        yield ['2012-0-11', 'date'];
+        yield ['2012-10-1', 'date'];
 
-            ['24:01:00', 'time'],
-            ['00:00:60', 'time'],
-            ['25:00:00', 'time'],
+        yield ['24:01:00', 'time'];
+        yield ['00:00:60', 'time'];
+        yield ['25:00:00', 'time'];
 
-            ['invalid_value_2000-05-01T12:12:12Z', 'date-time'],
-            ['2000-05-01T12:12:12Z_invalid_value', 'date-time'],
-            ['1999-1-11T00:00:00Z', 'date-time'],
-            ['1999-01-11T00:00:00+100', 'date-time'],
-            ['1999-01-11T00:00:00+1:00', 'date-time'],
-            ['1999.000Z-01-11T00:00:00+1:00', 'date-time'],
+        yield ['invalid_value_2000-05-01T12:12:12Z', 'date-time'];
+        yield ['2000-05-01T12:12:12Z_invalid_value', 'date-time'];
+        yield ['1999-1-11T00:00:00Z', 'date-time'];
+        yield ['1999-01-11T00:00:00+100', 'date-time'];
+        yield ['1999-01-11T00:00:00+1:00', 'date-time'];
+        yield ['1999.000Z-01-11T00:00:00+1:00', 'date-time'];
 
-            [PHP_INT_MAX, 'utc-millisec'],
+        yield [PHP_INT_MAX, 'utc-millisec'];
 
-            ['grey', 'color'],
-            ['#HHH', 'color'],
-            ['#000a', 'color'],
-            ['#aa', 'color'],
+        yield ['grey', 'color'];
+        yield ['#HHH', 'color'];
+        yield ['#000a', 'color'];
+        yield ['#aa', 'color'];
 
-            ['background; blue', 'style'],
+        yield ['background; blue', 'style'];
 
-            ['1 123 4424', 'phone'],
+        yield ['1 123 4424', 'phone'];
 
-            ['htt:/bluebox.org', 'uri'],
-            ['.relative:path/reference/', 'uri'],
-            ['', 'uri'],
-            ['//bluebox.org', 'uri'],
-            ['/absolutePathReference/', 'uri'],
-            ['./relativePathReference/', 'uri'],
-            ['./relative:PathReference/', 'uri'],
-            ['relativePathReference/', 'uri'],
-            ['relative/Path:Reference/', 'uri'],
+        yield ['htt:/bluebox.org', 'uri'];
+        yield ['.relative:path/reference/', 'uri'];
+        yield ['', 'uri'];
+        yield ['//bluebox.org', 'uri'];
+        yield ['/absolutePathReference/', 'uri'];
+        yield ['./relativePathReference/', 'uri'];
+        yield ['./relative:PathReference/', 'uri'];
+        yield ['relativePathReference/', 'uri'];
+        yield ['relative/Path:Reference/', 'uri'];
 
-            ['info@somewhere', 'email'],
+        yield ['info@somewhere', 'email'];
 
-            ['256.2.2.2', 'ip-address'],
+        yield ['256.2.2.2', 'ip-address'];
 
-            [':::ff', 'ipv6'],
+        yield [':::ff', 'ipv6'];
 
-            ['@localhost', 'host-name'],
-            ['..nohost', 'host-name'],
-        ];
+        yield ['@localhost', 'host-name'];
+        yield ['..nohost', 'host-name'];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{ "counter": "10" }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "counter": {
-                            "type": "string",
-                            "format": "regex",
-                            "pattern": "[0-9]+"
-                        }
+        yield [
+            '{ "counter": "10" }',
+            '{
+                "type": "object",
+                "properties": {
+                    "counter": {
+                        "type": "string",
+                        "format": "regex",
+                        "pattern": "[0-9]+"
                     }
-                }'],
+                }
+            }'
         ];
     }
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{ "counter": "blue" }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "counter": {
-                            "type": "string",
-                            "format": "regex",
-                            "pattern": "[0-9]+"
-                        }
+        yield [
+            '{ "counter": "blue" }',
+            '{
+                "type": "object",
+                "properties": {
+                    "counter": {
+                        "type": "string",
+                        "format": "regex",
+                        "pattern": "[0-9]+"
                     }
-                }'
-            ],
-            [
-                '{ "color": "blueberry" }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "color": {
-                            "type": "string",
-                            "format": "color"
-                        }
+                }
+            }'
+        ];
+        yield [
+            '{ "color": "blueberry" }',
+            '{
+                "type": "object",
+                "properties": {
+                    "color": {
+                        "type": "string",
+                        "format": "color"
                     }
-                }'
-            ]
+                }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/LongArraysTest.php b/tests/Constraints/LongArraysTest.php
index 8b8c88f0..d5289fed 100644
--- a/tests/Constraints/LongArraysTest.php
+++ b/tests/Constraints/LongArraysTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -60,7 +55,7 @@ public function testLongNumberArray(): void
 
         $tmp = new \stdClass();
         $tmp->p_array = array_map(function ($i) {
-            return rand(1, 1000) / 1000.0;
+            return random_int(1, 1000) / 1000.0;
         }, range(1, 100000));
         $input = json_encode($tmp);
 
diff --git a/tests/Constraints/MinItemsMaxItemsTest.php b/tests/Constraints/MinItemsMaxItemsTest.php
index df6f0c75..c096d675 100644
--- a/tests/Constraints/MinItemsMaxItemsTest.php
+++ b/tests/Constraints/MinItemsMaxItemsTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -13,89 +8,86 @@
 
 class MinItemsMaxItemsTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            'Input violating minItems constraint' => [
-                'input' => '{
-                  "value":[2]
-                }',
-                'schema' => '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"array","minItems":2,"maxItems":4}
-                  }
-                }',
-                'checkMode' => Constraint::CHECK_MODE_NORMAL,
-                [[
-                    'property' => 'value',
-                    'pointer' => '/value',
-                    'message' => 'There must be a minimum of 2 items in the array, 1 found',
-                    'constraint' => [
-                        'name' => 'minItems',
-                        'params' => [
-                            'minItems' => 2,
-                            'found' => 1
-                        ]
-                    ],
-                    'context' => 1
-                ]]
-            ],
-            'Input violating maxItems constraint' => [
-                'input' => '{
-                  "value":[2,2,5,8,5]
-                }',
-                'schema' => '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"array","minItems":2,"maxItems":4}
-                  }
-                }',
-                'checkMode' => Constraint::CHECK_MODE_NORMAL,
-                [[
-                    'property' => 'value',
-                    'pointer' => '/value',
-                    'message' => 'There must be a maximum of 4 items in the array, 5 found',
-                    'constraint' => [
-                        'name' => 'maxItems',
-                        'params' => [
-                            'maxItems' => 4,
-                            'found' => 5
-                        ]
-                    ],
-                    'context' => 1
-                ]]
-            ]
+        yield 'Input violating minItems constraint' => [
+            'input' => '{
+              "value":[2]
+            }',
+            'schema' => '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"array","minItems":2,"maxItems":4}
+              }
+            }',
+            'checkMode' => Constraint::CHECK_MODE_NORMAL,
+            [[
+                'property' => 'value',
+                'pointer' => '/value',
+                'message' => 'There must be a minimum of 2 items in the array, 1 found',
+                'constraint' => [
+                    'name' => 'minItems',
+                    'params' => [
+                        'minItems' => 2,
+                        'found' => 1
+                    ]
+                ],
+                'context' => 1
+            ]]
+        ];
+        yield 'Input violating maxItems constraint' => [
+            'input' => '{
+              "value":[2,2,5,8,5]
+            }',
+            'schema' => '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"array","minItems":2,"maxItems":4}
+              }
+            }',
+            'checkMode' => Constraint::CHECK_MODE_NORMAL,
+            [[
+                'property' => 'value',
+                'pointer' => '/value',
+                'message' => 'There must be a maximum of 4 items in the array, 5 found',
+                'constraint' => [
+                    'name' => 'maxItems',
+                    'params' => [
+                        'maxItems' => 4,
+                        'found' => 5
+                    ]
+                ],
+                'context' => 1
+            ]]
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":[2,2]
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"array","minItems":2,"maxItems":4}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "value":[2,2,5,8]
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"array","minItems":2,"maxItems":4}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "value":[2,2]
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"array","minItems":2,"maxItems":4}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "value":[2,2,5,8]
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"array","minItems":2,"maxItems":4}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/MinLengthMaxLengthMultiByteTest.php b/tests/Constraints/MinLengthMaxLengthMultiByteTest.php
index ab6db1a3..38b2bc5e 100644
--- a/tests/Constraints/MinLengthMaxLengthMultiByteTest.php
+++ b/tests/Constraints/MinLengthMaxLengthMultiByteTest.php
@@ -1,16 +1,12 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class MinLengthMaxLengthMultiByteTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
     protected function setUp(): void
@@ -20,59 +16,55 @@ protected function setUp(): void
         }
     }
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"☀"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","minLength":2,"maxLength":4}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "value":"☀☁☂☃☺"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","minLength":2,"maxLength":4}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "value":"☀"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","minLength":2,"maxLength":4}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "value":"☀☁☂☃☺"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","minLength":2,"maxLength":4}
+              }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"☀☁"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","minLength":2,"maxLength":4}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "value":"☀☁☂☃"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","minLength":2,"maxLength":4}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "value":"☀☁"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","minLength":2,"maxLength":4}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "value":"☀☁☂☃"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","minLength":2,"maxLength":4}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/MinLengthMaxLengthTest.php b/tests/Constraints/MinLengthMaxLengthTest.php
index 4832dfd5..04a0c25b 100644
--- a/tests/Constraints/MinLengthMaxLengthTest.php
+++ b/tests/Constraints/MinLengthMaxLengthTest.php
@@ -1,71 +1,63 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class MinLengthMaxLengthTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"w"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","minLength":2,"maxLength":4}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "value":"wo7us"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","minLength":2,"maxLength":4}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "value":"w"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","minLength":2,"maxLength":4}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "value":"wo7us"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","minLength":2,"maxLength":4}
+              }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"wo"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","minLength":2,"maxLength":4}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "value":"wo7u"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","minLength":2,"maxLength":4}
-                  }
-                }'
-            ],
+        yield [
+            '{
+              "value":"wo"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","minLength":2,"maxLength":4}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "value":"wo7u"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","minLength":2,"maxLength":4}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/MinMaxPropertiesTest.php b/tests/Constraints/MinMaxPropertiesTest.php
index 2de94329..4fb5e195 100644
--- a/tests/Constraints/MinMaxPropertiesTest.php
+++ b/tests/Constraints/MinMaxPropertiesTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -13,139 +8,130 @@
 
 class MinMaxPropertiesTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    /**
-     * {@inheritdoc}
-     */
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            'Empty object with minProperties: 0' => [
-                'input' => '{
-                  "value": {}
-                }',
-                'schema' => '{
-                  "type": "object",
-                  "properties": {
-                    "value": {"type": "object", "minProperties": 0}
-                  }
-                }'
-            ],
-            'Empty object with maxProperties: 1' => [
-                'input' => '{
-                  "value": {}
-                }',
-                'schema' => '{
-                  "type": "object",
-                  "properties": {
-                    "value": {"type": "object", "maxProperties": 1}
-                  }
-                }'
-            ],
-            'Empty object with minProperties: 0 and maxProperties: 1' => [
-                'input' => '{
-                  "value": {}
-                }',
-                'schema' => '{
-                  "type": "object",
-                  "properties": {
-                    "value": {"type": "object", "minProperties": 0,"maxProperties": 1}
-                  }
-                }'
-            ],
-            'Object with two properties with minProperties: 1 and maxProperties: 2' => [
-                'input' => '{
-                  "value": {"foo": 1, "bar": 2}
-                }',
-                'schema' => '{
-                  "type": "object",
-                  "properties": {
-                    "value": {"type": "object", "minProperties": 1,"maxProperties": 2}
-                  }
-                }'
-            ],
-            'Empty array with minProperties: 1 and maxProperties: 2' => [
-                'input' => '{
-                  "value": []
-                }',
-                'schema' => '{
-                  "properties": {
-                    "value": {"minProperties": 1,"maxProperties": 2}
-                  }
-                }',
-                'checkMode' => Constraint::CHECK_MODE_NORMAL,
-            ],
-            'Array with two items with maxProperties: 1' => [
-                'input' => '{
-                  "value": [1, 2]
-                }',
-                'schema' => '{
-                  "properties": {
-                    "value": {"maxProperties": 1}
-                  }
-                }'
-            ],
+        yield 'Empty object with minProperties: 0' => [
+            'input' => '{
+              "value": {}
+            }',
+            'schema' => '{
+              "type": "object",
+              "properties": {
+                "value": {"type": "object", "minProperties": 0}
+              }
+            }'
+        ];
+        yield 'Empty object with maxProperties: 1' => [
+            'input' => '{
+              "value": {}
+            }',
+            'schema' => '{
+              "type": "object",
+              "properties": {
+                "value": {"type": "object", "maxProperties": 1}
+              }
+            }'
+        ];
+        yield 'Empty object with minProperties: 0 and maxProperties: 1' => [
+            'input' => '{
+              "value": {}
+            }',
+            'schema' => '{
+              "type": "object",
+              "properties": {
+                "value": {"type": "object", "minProperties": 0,"maxProperties": 1}
+              }
+            }'
+        ];
+        yield 'Object with two properties with minProperties: 1 and maxProperties: 2' => [
+            'input' => '{
+              "value": {"foo": 1, "bar": 2}
+            }',
+            'schema' => '{
+              "type": "object",
+              "properties": {
+                "value": {"type": "object", "minProperties": 1,"maxProperties": 2}
+              }
+            }'
+        ];
+        yield 'Empty array with minProperties: 1 and maxProperties: 2' => [
+            'input' => '{
+              "value": []
+            }',
+            'schema' => '{
+              "properties": {
+                "value": {"minProperties": 1,"maxProperties": 2}
+              }
+            }',
+            'checkMode' => Constraint::CHECK_MODE_NORMAL,
+        ];
+        yield 'Array with two items with maxProperties: 1' => [
+            'input' => '{
+              "value": [1, 2]
+            }',
+            'schema' => '{
+              "properties": {
+                "value": {"maxProperties": 1}
+              }
+            }'
         ];
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            'Empty object with minProperties: 1' => [
-                'input' => '{
-                  "value": {}
-                }',
-                'schema' => '{
-                  "type": "object",
-                  "properties": {
-                    "value": {"type": "object", "minProperties": 1}
-                  }
-                }'
-            ],
-            'Empty object with minProperties' => [
-                'input' => '{}',
-                'schema' => '{
-                  "type": "object",
-                  "properties": {
-                    "propertyOne": {
-                      "type": "string"
-                    },
-                    "propertyTwo": {
-                      "type": "string"
-                    }
-                  },
-                  "minProperties": 1
-                }'
-            ],
-            'Object with two properties with maxProperties: 1' => [
-                'input' => '{
-                  "value": {
-                    "propertyOne": "valueOne",
-                    "propertyTwo": "valueTwo"
-                  }
-                }',
-                'schema' => '{
-                  "type": "object",
-                  "properties": {
-                    "value": {"type": "object", "maxProperties": 1}
-                  }
-                }'
-            ],
-            'Object with two properties with minProperties: 1 and maxProperties: 2' => [
-                'input' => '{
-                  "value": {"foo": 1, "bar": 2, "baz": 3}
-                }',
-                'schema' => '{
-                  "type": "object",
-                  "properties": {
-                    "value": {"type": "object", "minProperties": 1,"maxProperties": 2}
-                  }
-                }'
-            ],
+        yield 'Empty object with minProperties: 1' => [
+            'input' => '{
+              "value": {}
+            }',
+            'schema' => '{
+              "type": "object",
+              "properties": {
+                "value": {"type": "object", "minProperties": 1}
+              }
+            }'
+        ];
+        yield 'Empty object with minProperties' => [
+            'input' => '{}',
+            'schema' => '{
+              "type": "object",
+              "properties": {
+                "propertyOne": {
+                  "type": "string"
+                },
+                "propertyTwo": {
+                  "type": "string"
+                }
+              },
+              "minProperties": 1
+            }'
+        ];
+        yield 'Object with two properties with maxProperties: 1' => [
+            'input' => '{
+              "value": {
+                "propertyOne": "valueOne",
+                "propertyTwo": "valueTwo"
+              }
+            }',
+            'schema' => '{
+              "type": "object",
+              "properties": {
+                "value": {"type": "object", "maxProperties": 1}
+              }
+            }'
+        ];
+        yield 'Object with two properties with minProperties: 1 and maxProperties: 2' => [
+            'input' => '{
+              "value": {"foo": 1, "bar": 2, "baz": 3}
+            }',
+            'schema' => '{
+              "type": "object",
+              "properties": {
+                "value": {"type": "object", "minProperties": 1,"maxProperties": 2}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/MinimumMaximumTest.php b/tests/Constraints/MinimumMaximumTest.php
index 6f66565b..3573ed36 100644
--- a/tests/Constraints/MinimumMaximumTest.php
+++ b/tests/Constraints/MinimumMaximumTest.php
@@ -1,176 +1,168 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class MinimumMaximumTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":2
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"integer","minimum":4}
-                  }
-                }'
-            ],
-            [
-                '{"value": 3}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "minimum": 3, "exclusiveMinimum": true}
-                    }
-                }'
-            ],
-            [
-                '{
-                  "value":16
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"integer","maximum":8}
-                  }
-                }'
-            ],
-            [
-                '{"value": 8}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "maximum": 8, "exclusiveMaximum": true}
-                    }
-                }'
-            ],
-            [
-                '{"value": 4}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "exclusiveMinimum": true}
-                    }
-                }'
-            ],
-            [
-                '{"value": 4}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "exclusiveMaximum": true}
-                    }
-                }'
-            ],
-            [
-                '{"value": 4}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "minimum": 5, "exclusiveMinimum": false}
-                    }
-                }'
-            ],
-            [
-                '{"value": 4}',
-                '{
-                    "properties": {
-                        "value": {"type": "integer", "maximum": 3, "exclusiveMaximum": false}
-                    }
-                }'
-            ],
-            [
-                '{"value": 0.00}',
-                '{
-                    "properties": {
-                        "value": {"type": "number", "minimum": 0, "exclusiveMinimum": true}
-                    }
-                }'
-            ],
-            [
-                '{"value": 0.00}',
-                '{
-                    "properties": {
-                        "value": {"type": "number", "maximum": 0, "exclusiveMaximum": true}
-                    }
-                }'
-            ]
+        yield [
+            '{
+              "value":2
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"integer","minimum":4}
+              }
+            }'
+        ];
+        yield [
+            '{"value": 3}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "minimum": 3, "exclusiveMinimum": true}
+                }
+            }'
+        ];
+        yield [
+            '{
+              "value":16
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"integer","maximum":8}
+              }
+            }'
+        ];
+        yield [
+            '{"value": 8}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "maximum": 8, "exclusiveMaximum": true}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 4}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "exclusiveMinimum": true}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 4}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "exclusiveMaximum": true}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 4}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "minimum": 5, "exclusiveMinimum": false}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 4}',
+            '{
+                "properties": {
+                    "value": {"type": "integer", "maximum": 3, "exclusiveMaximum": false}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 0.00}',
+            '{
+                "properties": {
+                    "value": {"type": "number", "minimum": 0, "exclusiveMinimum": true}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 0.00}',
+            '{
+                "properties": {
+                    "value": {"type": "number", "maximum": 0, "exclusiveMaximum": true}
+                }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":6
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"integer","minimum":4}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "value":6
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"integer","maximum":8}
-                  }
-                }'
-            ],
-            [
-                '{"value": 6}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "minimum": 6, "exclusiveMinimum": false}
-                    }
-                }'
-            ],
-            [
-                '{"value": 6}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "maximum": 6, "exclusiveMaximum": false}
-                    }
-                }'
-            ],
-            [
-                '{"value": 6}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "minimum": 6}
-                    }
-                }'
-            ],
-            [
-                '{"value": 6}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "integer", "maximum": 6}
-                    }
-                }'
-            ]
+        yield [
+            '{
+              "value":6
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"integer","minimum":4}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "value":6
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"integer","maximum":8}
+              }
+            }'
+        ];
+        yield [
+            '{"value": 6}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "minimum": 6, "exclusiveMinimum": false}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 6}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "maximum": 6, "exclusiveMaximum": false}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 6}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "minimum": 6}
+                }
+            }'
+        ];
+        yield [
+            '{"value": 6}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "integer", "maximum": 6}
+                }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/NotTest.php b/tests/Constraints/NotTest.php
index 2b6b48e3..4a7f189c 100644
--- a/tests/Constraints/NotTest.php
+++ b/tests/Constraints/NotTest.php
@@ -1,102 +1,94 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class NotTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                    "x": [1, 2]
-                }',
-                '{
-                    "properties": {
-                        "x": {
-                            "not": {
-                                "type": "array",
-                                "items": {"type": "integer"},
-                                "minItems": 2
-                            }
+        yield [
+            '{
+                "x": [1, 2]
+            }',
+            '{
+                "properties": {
+                    "x": {
+                        "not": {
+                            "type": "array",
+                            "items": {"type": "integer"},
+                            "minItems": 2
                         }
                     }
-                }'
-            ],
-            [ // check that a missing, required property is correctly validated
-                '{"y": "foo"}',
-                '{
-                    "type": "object",
-                    "required": ["x"],
-                    "properties": {
-                        "x": {
-                            "not": {
-                                "type": "null"
-                            }
+                }
+            }'
+        ];
+        yield 'check that a missing, required property is correctly validated' => [
+            '{"y": "foo"}',
+            '{
+                "type": "object",
+                "required": ["x"],
+                "properties": {
+                    "x": {
+                        "not": {
+                            "type": "null"
                         }
                     }
-                }'
-            ]
+                }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                    "x": [1]
-                }',
-                '{
-                    "properties": {
-                        "x": {
-                            "not": {
-                                "type": "array",
-                                "items": {"type": "integer"},
-                                "minItems": 2
-                            }
+        yield [
+            '{
+                "x": [1]
+            }',
+            '{
+                "properties": {
+                    "x": {
+                        "not": {
+                            "type": "array",
+                            "items": {"type": "integer"},
+                            "minItems": 2
                         }
                     }
-                }'
-            ],
-            [
-                '{
-                    "x": ["foo", 2]
-                }',
-                '{
-                    "properties": {
-                        "x": {
-                            "not": {
-                                "type": "array",
-                                "items": {"type": "integer"},
-                                "minItems": 2
-                            }
+                }
+            }'
+        ];
+        yield [
+            '{
+                "x": ["foo", 2]
+            }',
+            '{
+                "properties": {
+                    "x": {
+                        "not": {
+                            "type": "array",
+                            "items": {"type": "integer"},
+                            "minItems": 2
                         }
                     }
-                }'
-            ],
-            [ // check that a missing, non-required property isn't validated
-                '{"y": "foo"}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "x": {
-                            "not": {
-                                "type": "null"
-                            }
+                }
+            }'
+        ];
+        yield "check that a missing, non-required property isn't validated" => [
+            '{"y": "foo"}',
+            '{
+                "type": "object",
+                "properties": {
+                    "x": {
+                        "not": {
+                            "type": "null"
                         }
                     }
-                }'
-            ]
+                }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/NumberAndIntegerTypesTest.php b/tests/Constraints/NumberAndIntegerTypesTest.php
index 78b02110..c09abee8 100644
--- a/tests/Constraints/NumberAndIntegerTypesTest.php
+++ b/tests/Constraints/NumberAndIntegerTypesTest.php
@@ -1,118 +1,110 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class NumberAndIntegerTypesTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "integer": 1.4
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "integer":{"type":"integer"}
-                  }
-                }'
-            ],
-            [
-                '{"integer": 1.001}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "integer": {"type": "integer"}
-                    }
-                }'
-            ],
-            [
-                '{"integer": true}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "integer": {"type": "integer"}
-                    }
-                }'
-            ],
-            [
-                '{"number": "x"}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "number": {"type": "number"}
-                    }
-                }'
-            ]
+        yield [
+            '{
+              "integer": 1.4
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "integer":{"type":"integer"}
+              }
+            }'
+        ];
+        yield [
+            '{"integer": 1.001}',
+            '{
+                "type": "object",
+                "properties": {
+                    "integer": {"type": "integer"}
+                }
+            }'
+        ];
+        yield [
+            '{"integer": true}',
+            '{
+                "type": "object",
+                "properties": {
+                    "integer": {"type": "integer"}
+                }
+            }'
+        ];
+        yield [
+            '{"number": "x"}',
+            '{
+                "type": "object",
+                "properties": {
+                    "number": {"type": "number"}
+                }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "integer": 1
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "integer":{"type":"integer"}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "number": 1.4
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "number":{"type":"number"}
-                  }
-                }'
-            ],
-            [
-                '{"number": 1e5}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "number": {"type": "number"}
-                    }
-                }'
-            ],
-            [
-                '{"number": 1}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "number": {"type": "number"}
+        yield [
+            '{
+              "integer": 1
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "integer":{"type":"integer"}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "number": 1.4
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "number":{"type":"number"}
+              }
+            }'
+        ];
+        yield [
+            '{"number": 1e5}',
+            '{
+                "type": "object",
+                "properties": {
+                    "number": {"type": "number"}
+                }
+            }'
+        ];
+        yield [
+            '{"number": 1}',
+            '{
+                "type": "object",
+                "properties": {
+                    "number": {"type": "number"}
 
+                }
+            }'
+        ];
+        yield [
+            '{"number": -49.89}',
+            '{
+                "type": "object",
+                "properties": {
+                    "number": {
+                      "type": "number",
+                      "multipleOf": 0.01
                     }
-                }'
-            ],
-            [
-                '{"number": -49.89}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "number": {
-                          "type": "number",
-                          "multipleOf": 0.01
-                        }
-                    }
-                }'
-            ]
+                }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/OfPropertiesTest.php b/tests/Constraints/OfPropertiesTest.php
index b602c0b4..04ca060b 100644
--- a/tests/Constraints/OfPropertiesTest.php
+++ b/tests/Constraints/OfPropertiesTest.php
@@ -1,240 +1,231 @@
 <?php
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 use JsonSchema\Constraints\Constraint;
 use JsonSchema\Validator;
 
-/**
- * Class OfPropertiesTest
- */
 class OfPropertiesTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{"prop1": "abc"}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {"type": "string"},
-                    "prop2": {
-                      "oneOf": [
-                        {"type": "number"},
-                        {"type": "string"}
-                      ]
-                    }
-                  },
-                  "required": ["prop1"]
-                }'
-            ],
-            [
-                '{"prop1": "abc", "prop2": 23}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {"type": "string"},
-                    "prop2": {
-                      "oneOf": [
-                        {"type": "number"},
-                        {"type": "string"}
-                      ]
-                    }
-                  },
-                  "required": ["prop1"]
-                }'
-            ],
+        yield [
+            '{"prop1": "abc"}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {"type": "string"},
+                "prop2": {
+                  "oneOf": [
+                    {"type": "number"},
+                    {"type": "string"}
+                  ]
+                }
+              },
+              "required": ["prop1"]
+            }'
+        ];
+        yield [
+            '{"prop1": "abc", "prop2": 23}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {"type": "string"},
+                "prop2": {
+                  "oneOf": [
+                    {"type": "number"},
+                    {"type": "string"}
+                  ]
+                }
+              },
+              "required": ["prop1"]
+            }'
         ];
     }
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
+        yield [
+            '{"prop1": "abc", "prop2": []}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {"type": "string"},
+                "prop2": {
+                  "oneOf": [
+                    {"type": "number"},
+                    {"type": "string"}
+                  ]
+                }
+              },
+              "required": ["prop1"]
+            }',
+            null,
             [
-                '{"prop1": "abc", "prop2": []}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {"type": "string"},
-                    "prop2": {
-                      "oneOf": [
-                        {"type": "number"},
-                        {"type": "string"}
-                      ]
-                    }
-                  },
-                  "required": ["prop1"]
-                }',
-                null,
                 [
-                    [
-                        'property'   => 'prop2',
-                        'pointer'    => '/prop2',
-                        'message'    => 'Array value found, but a string is required',
-                        'constraint' => [
-                            'name' => 'type',
-                            'params' => [
-                                'expected'   => 'a string',
-                                'found'      => 'array'
-                            ]
-                        ],
-                        'context'    => Validator::ERROR_DOCUMENT_VALIDATION
+                    'property'   => 'prop2',
+                    'pointer'    => '/prop2',
+                    'message'    => 'Array value found, but a string is required',
+                    'constraint' => [
+                        'name' => 'type',
+                        'params' => [
+                            'expected'   => 'a string',
+                            'found'      => 'array'
+                        ]
                     ],
-                    [
-                        'property'   => 'prop2',
-                        'pointer'    => '/prop2',
-                        'message'    => 'Array value found, but a number is required',
-                        'constraint' => [
-                            'name' => 'type',
-                            'params' => [
-                                'expected'   => 'a number',
-                                'found'      => 'array'
-                            ]
-                        ],
-                        'context'    => Validator::ERROR_DOCUMENT_VALIDATION
+                    'context'    => Validator::ERROR_DOCUMENT_VALIDATION
+                ],
+                [
+                    'property'   => 'prop2',
+                    'pointer'    => '/prop2',
+                    'message'    => 'Array value found, but a number is required',
+                    'constraint' => [
+                        'name' => 'type',
+                        'params' => [
+                            'expected'   => 'a number',
+                            'found'      => 'array'
+                        ]
                     ],
-                    [
-                        'property'   => 'prop2',
-                        'pointer'    => '/prop2',
-                        'message'    => 'Failed to match exactly one schema',
-                        'constraint' => [
-                            'name' => 'oneOf',
-                            'params' => []
-                        ],
-                        'context'    => Validator::ERROR_DOCUMENT_VALIDATION
+                    'context'    => Validator::ERROR_DOCUMENT_VALIDATION
+                ],
+                [
+                    'property'   => 'prop2',
+                    'pointer'    => '/prop2',
+                    'message'    => 'Failed to match exactly one schema',
+                    'constraint' => [
+                        'name' => 'oneOf',
+                        'params' => []
                     ],
+                    'context'    => Validator::ERROR_DOCUMENT_VALIDATION
                 ],
             ],
-            [
-                '{"prop1": [1,2]}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {
-                      "oneOf": [
-                        {
-                          "type": "string",
-                          "pattern": "^[a-z]*$"
-                        },
-                        {
-                          "type": "string",
-                          "pattern": "^[A-Z]*$"
-                        }
-                      ]
+        ];
+        yield [
+            '{"prop1": [1,2]}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {
+                  "oneOf": [
+                    {
+                      "type": "string",
+                      "pattern": "^[a-z]*$"
+                    },
+                    {
+                      "type": "string",
+                      "pattern": "^[A-Z]*$"
                     }
-                  }
-                }'
-            ],
-            [
-                '{"prop1": [1,2]}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {
-                      "anyOf": [
-                        {
-                          "type": "string",
-                          "pattern": "^[A-Z]*$"
-                        }
-                      ]
+                  ]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"prop1": [1,2]}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {
+                  "anyOf": [
+                    {
+                      "type": "string",
+                      "pattern": "^[A-Z]*$"
                     }
-                  }
-                }'
-            ],
-            [
-                '{"prop1": [1,2]}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {
-                      "anyOf": [
-                        {
-                          "type": "number"
-                        },
-                        {
-                          "type": "string",
-                          "pattern": "^[A-Z]*$"
-                        }
-                      ]
+                  ]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"prop1": [1,2]}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {
+                  "anyOf": [
+                    {
+                      "type": "number"
+                    },
+                    {
+                      "type": "string",
+                      "pattern": "^[A-Z]*$"
                     }
-                  }
-                }'
-            ],
-            [
-                '{"prop1": [1,2]}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {
-                      "anyOf": [
-                        {
-                          "type": "string"
-                        },
-                        {
-                          "type": "string",
-                          "pattern": "^[A-Z]*$"
-                        }
-                      ]
+                  ]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"prop1": [1,2]}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {
+                  "anyOf": [
+                    {
+                      "type": "string"
+                    },
+                    {
+                      "type": "string",
+                      "pattern": "^[A-Z]*$"
                     }
-                  }
-                }'
-            ],
-            [
-                '{"prop1": [1,2]}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {
-                      "anyOf": [
-                        {
-                          "type": "string",
-                          "pattern": "^[a-z]*$"
-                        },
-                        {
-                          "type": "string",
-                          "pattern": "^[A-Z]*$"
-                        }
-                      ]
+                  ]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"prop1": [1,2]}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {
+                  "anyOf": [
+                    {
+                      "type": "string",
+                      "pattern": "^[a-z]*$"
+                    },
+                    {
+                      "type": "string",
+                      "pattern": "^[A-Z]*$"
                     }
-                  }
-                }'
-            ],
-            [
-                '{"prop1": [1,2]}',
-                '{
-                  "type": "object",
-                  "properties": {
-                    "prop1": {
-                      "anyOf": [
-                        {
-                          "type": "number"
-                        },
-                        {
-                          "type": "string"
-                        },
-                        {
-                          "type": "string"
-                        }
-                      ]
+                  ]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"prop1": [1,2]}',
+            '{
+              "type": "object",
+              "properties": {
+                "prop1": {
+                  "anyOf": [
+                    {
+                      "type": "number"
+                    },
+                    {
+                      "type": "string"
+                    },
+                    {
+                      "type": "string"
                     }
-                  }
-                }'
-            ]
+                  ]
+                }
+              }
+            }'
         ];
     }
 
     public function testNoPrematureAnyOfException(): void
     {
-        $schema = json_decode('{
+        $schema = json_decode(
+            '{
             "type": "object",
             "properties": {
                 "propertyOne": {
@@ -244,8 +235,10 @@ public function testNoPrematureAnyOfException(): void
                     ]
                 }
             }
-        }');
-        $data = json_decode('{"propertyOne":"ABC"}');
+        }',
+            false
+        );
+        $data = json_decode('{"propertyOne":"ABC"}', false);
 
         $v = new Validator();
         $v->validate($data, $schema, Constraint::CHECK_MODE_EXCEPTIONS);
@@ -254,7 +247,8 @@ public function testNoPrematureAnyOfException(): void
 
     public function testNoPrematureOneOfException(): void
     {
-        $schema = json_decode('{
+        $schema = json_decode(
+            '{
             "type": "object",
             "properties": {
                 "propertyOne": {
@@ -264,8 +258,10 @@ public function testNoPrematureOneOfException(): void
                     ]
                 }
             }
-        }');
-        $data = json_decode('{"propertyOne":"ABC"}');
+        }',
+            false
+        );
+        $data = json_decode('{"propertyOne":"ABC"}', false);
 
         $v = new Validator();
         $v->validate($data, $schema, Constraint::CHECK_MODE_EXCEPTIONS);
diff --git a/tests/Constraints/PatternPropertiesTest.php b/tests/Constraints/PatternPropertiesTest.php
index 526777ef..ca99fc47 100644
--- a/tests/Constraints/PatternPropertiesTest.php
+++ b/tests/Constraints/PatternPropertiesTest.php
@@ -1,214 +1,200 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class PatternPropertiesTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            // matches pattern but invalid schema for object
-            [
-                json_encode([
-                    'someobject' => [
-                        'foobar' => 'foo',
-                        'barfoo' => 'bar',
-                    ]
-                ]),
-                json_encode([
-                    'type' => 'object',
-                    'patternProperties' => [
-                        '^someobject$' => [
-                            'type' => 'object',
-                            'additionalProperties' => false,
-                            'properties' => [
-                                'barfoo' => [
-                                    'type' => 'string',
-                                ],
-                            ]
+        yield 'matches pattern but invalid schema for object' => [
+            json_encode([
+                'someobject' => [
+                    'foobar' => 'foo',
+                    'barfoo' => 'bar',
+                ]
+            ]),
+            json_encode([
+                'type' => 'object',
+                'patternProperties' => [
+                    '^someobject$' => [
+                        'type' => 'object',
+                        'additionalProperties' => false,
+                        'properties' => [
+                            'barfoo' => [
+                                'type' => 'string',
+                            ],
                         ]
                     ]
-                ])
-            ],
-            // Does not match pattern
-            [
-                json_encode([
-                        'regex_us' => false,
-                ]),
-                json_encode([
-                        'type' => 'object',
-                        'patternProperties' => [
-                            '^[a-z]+_(jp|de)$' => [
-                                'type' => ['boolean']
-                            ]
-                        ],
-                        'additionalProperties' => false
-                ])
-            ],
-            // Does not match pattern with unicode
-            [
-                json_encode([
-                        '猡猡獛' => false,
-                ]),
-                json_encode([
-                        'type' => 'object',
-                        'patternProperties' => [
-                            '^[\\x{0080}-\\x{006FFF}]+$' => [
-                                'type' => ['boolean']
-                            ]
-                        ],
-                        'additionalProperties' => false
-                ])
-            ],
-            // An invalid regular expression pattern
-            [
-                json_encode([
-                        'regex_us' => false,
-                ]),
-                json_encode([
-                        'type' => 'object',
-                        'patternProperties' => [
-                            '^[a-z+_jp|de)$' => [
-                                'type' => ['boolean']
-                            ]
-                        ],
-                        'additionalProperties' => false
-                ])
-            ],
+                ]
+            ])
+        ];
+        yield 'Does not match pattern' => [
+            json_encode([
+                    'regex_us' => false,
+            ]),
+            json_encode([
+                'type' => 'object',
+                'patternProperties' => [
+                    '^[a-z]+_(jp|de)$' => [
+                        'type' => ['boolean']
+                    ]
+                ],
+                'additionalProperties' => false
+            ])
+        ];
+        yield 'Does not match pattern with unicode' => [
+            json_encode([
+                '猡猡獛' => false,
+            ]),
+            json_encode([
+                'type' => 'object',
+                'patternProperties' => [
+                    '^[\\x{0080}-\\x{006FFF}]+$' => [
+                        'type' => ['boolean']
+                    ]
+                ],
+                'additionalProperties' => false
+            ])
+        ];
+        yield 'An invalid regular expression pattern' => [
+            json_encode([
+                    'regex_us' => false,
+            ]),
+            json_encode([
+                'type' => 'object',
+                'patternProperties' => [
+                    '^[a-z+_jp|de)$' => [
+                        'type' => ['boolean']
+                    ]
+                ],
+                'additionalProperties' => false
+            ])
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                // validates pattern schema
-                json_encode([
-                    'someobject' => [
-                        'foobar' => 'foo',
-                        'barfoo' => 'bar',
-                    ],
-                    'someotherobject' => [
-                        'foobar' => 1234,
+        [
+            yield 'validates pattern schema' => json_encode([
+                'someobject' => [
+                    'foobar' => 'foo',
+                    'barfoo' => 'bar',
+                ],
+                'someotherobject' => [
+                    'foobar' => 1234,
+                ],
+                '/products' => [
+                    'get' => []
+                ],
+                '#products' => [
+                    'get' => []
+                ],
+                '+products' => [
+                    'get' => []
+                ],
+                '~products' => [
+                    'get' => []
+                ],
+                '*products' => [
+                    'get' => []
+                ],
+                '%products' => [
+                    'get' => []
+                ]
+            ]),
+            json_encode([
+                'type' => 'object',
+                'additionalProperties' => false,
+                'patternProperties' => [
+                    '^someobject$' => [
+                        'type' => 'object',
+                        'properties' => [
+                            'foobar' => ['type' => 'string'],
+                            'barfoo' => ['type' => 'string'],
+                        ],
                     ],
-                    '/products' => [
-                        'get' => []
+                    '^someotherobject$' => [
+                        'type' => 'object',
+                        'properties' => [
+                            'foobar' => ['type' => 'number'],
+                        ],
                     ],
-                    '#products' => [
-                        'get' => []
+                    '^/' => [
+                        'type' => 'object',
+                        'properties' => [
+                            'get' => ['type' => 'array']
+                        ]
                     ],
-                    '+products' => [
-                        'get' => []
+                    '^#' => [
+                        'type' => 'object',
+                        'properties' => [
+                            'get' => ['type' => 'array']
+                        ]
                     ],
-                    '~products' => [
-                        'get' => []
+                    '^\+' => [
+                        'type' => 'object',
+                        'properties' => [
+                            'get' => ['type' => 'array']
+                        ]
                     ],
-                    '*products' => [
-                        'get' => []
+                    '^~' => [
+                        'type' => 'object',
+                        'properties' => [
+                            'get' => ['type' => 'array']
+                        ]
                     ],
-                    '%products' => [
-                        'get' => []
-                    ]
-                ]),
-                json_encode([
-                    'type' => 'object',
-                    'additionalProperties' => false,
-                    'patternProperties' => [
-                        '^someobject$' => [
-                            'type' => 'object',
-                            'properties' => [
-                                'foobar' => ['type' => 'string'],
-                                'barfoo' => ['type' => 'string'],
-                            ],
-                        ],
-                        '^someotherobject$' => [
-                            'type' => 'object',
-                            'properties' => [
-                                'foobar' => ['type' => 'number'],
-                            ],
-                        ],
-                        '^/' => [
-                            'type' => 'object',
-                            'properties' => [
-                                'get' => ['type' => 'array']
-                            ]
-                        ],
-                        '^#' => [
-                            'type' => 'object',
-                            'properties' => [
-                                'get' => ['type' => 'array']
-                            ]
-                        ],
-                        '^\+' => [
-                            'type' => 'object',
-                            'properties' => [
-                                'get' => ['type' => 'array']
-                            ]
-                        ],
-                        '^~' => [
-                            'type' => 'object',
-                            'properties' => [
-                                'get' => ['type' => 'array']
-                            ]
-                        ],
-                        '^\*' => [
-                            'type' => 'object',
-                            'properties' => [
-                                'get' => ['type' => 'array']
-                            ]
-                        ],
-                        '^%' => [
-                            'type' => 'object',
-                            'properties' => [
-                                'get' => ['type' => 'array']
-                            ]
+                    '^\*' => [
+                        'type' => 'object',
+                        'properties' => [
+                            'get' => ['type' => 'array']
                         ]
-                    ]
-                ])
-            ],
-            [
-                json_encode([
-                        'foobar' => true,
-                        'regex_us' => 'foo',
-                        'regex_de' => 1234
-                ]),
-                json_encode([
+                    ],
+                    '^%' => [
                         'type' => 'object',
                         'properties' => [
-                            'foobar' => ['type' => 'boolean']
-                        ],
-                        'patternProperties' => [
-                            '^[a-z]+_(us|de)$' => [
-                                'type' => ['string', 'integer']
-                            ]
-                        ],
-                        'additionalProperties' => false
-                ])
-            ],
-            // Does match pattern with unicode
-            [
-                json_encode([
-                    'ðæſ' => 'unicode',
-                ]),
-                json_encode([
+                            'get' => ['type' => 'array']
+                        ]
+                    ]
+                ]
+            ])
+        ];
+        yield [
+            json_encode([
+                    'foobar' => true,
+                    'regex_us' => 'foo',
+                    'regex_de' => 1234
+            ]),
+            json_encode([
                     'type' => 'object',
+                    'properties' => [
+                        'foobar' => ['type' => 'boolean']
+                    ],
                     'patternProperties' => [
-                        '^[\\x{0080}-\\x{10FFFF}]+$' => [
-                            'type' => ['string']
+                        '^[a-z]+_(us|de)$' => [
+                            'type' => ['string', 'integer']
                         ]
                     ],
                     'additionalProperties' => false
-                ])
-            ],
+            ])
+        ];
+        yield 'Does match pattern with unicode' => [
+            json_encode([
+                'ðæſ' => 'unicode',
+            ]),
+            json_encode([
+                'type' => 'object',
+                'patternProperties' => [
+                    '^[\\x{0080}-\\x{10FFFF}]+$' => [
+                        'type' => ['string']
+                    ]
+                ],
+                'additionalProperties' => false
+            ])
         ];
     }
 }
diff --git a/tests/Constraints/PatternTest.php b/tests/Constraints/PatternTest.php
index 8207c91b..ee44d5fb 100644
--- a/tests/Constraints/PatternTest.php
+++ b/tests/Constraints/PatternTest.php
@@ -1,103 +1,95 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class PatternTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"Abacates"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","pattern":"^cat"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{"value": "abc"}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "string", "pattern": "^a*$"}
-                    },
-                    "additionalProperties": false
-                }'
-            ],
-            [
-                '{"value": "ü"}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "string", "pattern": "^ü$"}
-                    },
-                    "additionalProperties": false
-                }'
-            ],
+        yield [
+            '{
+              "value":"Abacates"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","pattern":"^cat"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{"value": "abc"}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "string", "pattern": "^a*$"}
+                },
+                "additionalProperties": false
+            }'
+        ];
+        yield [
+            '{"value": "ü"}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "string", "pattern": "^ü$"}
+                },
+                "additionalProperties": false
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "value":"Abacates"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","pattern":"tes$"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{
-                  "value":"Abacates"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "value":{"type":"string","pattern":"cat"}
-                  },
-                  "additionalProperties":false
-                }'
-            ],
-            [
-                '{"value": "aaa"}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "string", "pattern": "^a*$"}
-                    },
-                    "additionalProperties": false
-                }'
-            ],
-            [
-                '{"value": "↓æ→"}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "value": {"type": "string", "pattern": "^↓æ.$"}
-                    },
-                    "additionalProperties": false
-                }'
-            ]
+        yield [
+            '{
+              "value":"Abacates"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","pattern":"tes$"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{
+              "value":"Abacates"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "value":{"type":"string","pattern":"cat"}
+              },
+              "additionalProperties":false
+            }'
+        ];
+        yield [
+            '{"value": "aaa"}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "string", "pattern": "^a*$"}
+                },
+                "additionalProperties": false
+            }'
+        ];
+        yield [
+            '{"value": "↓æ→"}',
+            '{
+                "type": "object",
+                "properties": {
+                    "value": {"type": "string", "pattern": "^↓æ.$"}
+                },
+                "additionalProperties": false
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/PointerTest.php b/tests/Constraints/PointerTest.php
index 1623f41b..426b7c59 100644
--- a/tests/Constraints/PointerTest.php
+++ b/tests/Constraints/PointerTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
diff --git a/tests/Constraints/ReadOnlyTest.php b/tests/Constraints/ReadOnlyTest.php
index 3a54fa51..352bce81 100644
--- a/tests/Constraints/ReadOnlyTest.php
+++ b/tests/Constraints/ReadOnlyTest.php
@@ -1,48 +1,39 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class ReadOnlyTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        //is readonly really required?
-        return [
-            [
-                '{ "number": [] }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "number":{"type":"string","readonly":true}
-                  }
-                }'
-            ]
+        yield 'is readonly really required?' => [
+            '{ "number": [] }',
+            '{
+              "type":"object",
+              "properties":{
+                "number":{"type":"string","readonly":true}
+              }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "number": "1.4"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "number":{"type":"string","readonly":true}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "number": "1.4"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "number":{"type":"string","readonly":true}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/RequireTest.php b/tests/Constraints/RequireTest.php
index 34ca88ca..614f6276 100644
--- a/tests/Constraints/RequireTest.php
+++ b/tests/Constraints/RequireTest.php
@@ -1,52 +1,44 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class RequireTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "state":"DF"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "state":{"type":"string","requires":"city"},
-                    "city":{"type":"string"}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "state":"DF"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "state":{"type":"string","requires":"city"},
+                "city":{"type":"string"}
+              }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "state":"DF",
-                  "city":"Brasília"
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "state":{"type":"string","requires":"city"},
-                    "city":{"type":"string"}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "state":"DF",
+              "city":"Brasília"
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "state":{"type":"string","requires":"city"},
+                "city":{"type":"string"}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/RequiredPropertyTest.php b/tests/Constraints/RequiredPropertyTest.php
index 2f38c3e5..06fdedbd 100644
--- a/tests/Constraints/RequiredPropertyTest.php
+++ b/tests/Constraints/RequiredPropertyTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -14,29 +9,29 @@
 
 class RequiredPropertyTest extends BaseTestCase
 {
-    // Most tests are draft-03 compliant, but some tests are draft-04, or mix draft-03 and
-    // draft-04 syntax within the same schema. Unfortunately, draft-03 and draft-04 required
-    // definitions are incompatible, so disabling schema validation for these tests.
+    /**
+     * Most tests are draft-03 compliant, but some tests are draft-04, or mix draft-03 and
+     * draft-04 syntax within the same schema. Unfortunately, draft-03 and draft-04 required
+     * definitions are incompatible, so disabling schema validation for these tests.
+     *
+     * @var string
+     * */
     protected $schemaSpec = 'http://json-schema.org/draft-03/schema#';
-    protected $validateSchema = false;
 
     public function testErrorPropertyIsPopulatedForRequiredIfMissingInInput(): void
     {
         $validator = new UndefinedConstraint();
-        $document = json_decode(
-            '{
-            "bar": 42
-        }'
-        );
+        $document = json_decode('{ "bar": 42 }', false);
         $schema = json_decode(
             '{
-            "type": "object",
-            "properties": {
-                "foo": {"type": "number"},
-                "bar": {"type": "number"}
-            },
-            "required": ["foo"]
-        }'
+                "type": "object",
+                "properties": {
+                    "foo": {"type": "number"},
+                    "bar": {"type": "number"}
+                },
+                "required": ["foo"]
+            }',
+            false
         );
 
         $validator->check($document, $schema);
@@ -47,11 +42,7 @@ public function testErrorPropertyIsPopulatedForRequiredIfMissingInInput(): void
     public function testPathErrorPropertyIsPopulatedForRequiredIfMissingInInput(): void
     {
         $validator = new UndefinedConstraint();
-        $document = json_decode(
-            '{
-                "foo": [{"baz": 1.5}]
-            }'
-        );
+        $document = json_decode('{ "foo": [{"baz": 1.5}] }', false);
         $schema = json_decode(
             '{
                 "type": "object",
@@ -69,7 +60,8 @@ public function testPathErrorPropertyIsPopulatedForRequiredIfMissingInInput(): v
                     }
                 },
                 "required": ["foo"]
-            }'
+            }',
+            false
         );
 
         $validator->check($document, $schema);
@@ -80,21 +72,17 @@ public function testPathErrorPropertyIsPopulatedForRequiredIfMissingInInput(): v
     public function testErrorPropertyIsPopulatedForRequiredIfEmptyValueInInput(): void
     {
         $validator = new UndefinedConstraint();
-        $document = json_decode(
-            '{
-            "bar": 42,
-            "foo": null
-        }'
-        );
+        $document = json_decode('{ "bar": 42, "foo": null }', false);
         $schema = json_decode(
             '{
-            "type": "object",
-            "properties": {
-                "foo": {"type": "number"},
-                "bar": {"type": "number"}
-            },
-            "required": ["foo"]
-        }'
+                "type": "object",
+                "properties": {
+                    "foo": {"type": "number"},
+                    "bar": {"type": "number"}
+                },
+                "required": ["foo"]
+            }',
+            false
         );
 
         $validator->check($document, $schema);
@@ -113,329 +101,325 @@ protected function assertErrorHasExpectedPropertyValue($error, $propertyValue):
         $this->assertEquals($propertyValue, $error[0]['property']);
     }
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "number":{"type":"number","required":true}
-                  }
-                }'
-            ],
-            [
-                '{}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "number": {"type": "number"}
-                    },
-                    "required": ["number"]
-                }'
-            ],
-            [
-                '{
-                    "foo": {}
-                }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "foo": {
-                            "type": "object",
-                            "properties": {
-                                "bar": {"type": "number"}
-                            },
-                            "required": ["bar"]
-                        }
-                    }
-                }'
-            ],
-            [
-                '{
-                    "bar": 1.4
-                 }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "foo": {"type": "string", "required": true},
-                        "bar": {"type": "number"}
-                    },
-                    "required": ["bar"]
-                }'
-            ],
-            [
-                '{}',
-                '{
-                    "required": ["foo"]
-                }'
-            ],
-            [
-                '{
-                }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "foo": { "required": true }
+        yield [
+            '{}',
+            '{
+              "type":"object",
+              "properties":{
+                "number":{"type":"number","required":true}
+              }
+            }'
+        ];
+        yield [
+            '{}',
+            '{
+                "type": "object",
+                "properties": {
+                    "number": {"type": "number"}
+                },
+                "required": ["number"]
+            }'
+        ];
+        yield [
+            '{
+                "foo": {}
+            }',
+            '{
+                "type": "object",
+                "properties": {
+                    "foo": {
+                        "type": "object",
+                        "properties": {
+                            "bar": {"type": "number"}
+                        },
+                        "required": ["bar"]
                     }
-                }'
-            ],
-            [
-                '{
-                  "string":{}
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "string":{"type":"string", "required": true}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "number":{}
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "number":{"type":"number", "required": true}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "integer":{}
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "integer":{"type":"integer", "required": true}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "boolean":{}
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "boolean":{"type":"boolean", "required": true}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "array":{}
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "array":{"type":"array", "required": true}
-                  }
-                }',
-                Constraint::CHECK_MODE_NORMAL
-            ],
-            [
-                '{
-                  "null":{}
-                }',
-                '{
-                  "type":"object",
-                  "properties": {
-                    "null":{"type":"null", "required": true}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "foo": {"baz": 1.5}
-                }',
-                '{
+                }
+            }'
+        ];
+        yield [
+            '{
+                "bar": 1.4
+             }',
+            '{
+                "type": "object",
+                "properties": {
+                    "foo": {"type": "string", "required": true},
+                    "bar": {"type": "number"}
+                },
+                "required": ["bar"]
+            }'
+        ];
+        yield [
+            '{}',
+            '{
+                "required": ["foo"]
+            }'
+        ];
+        yield [
+            '{
+            }',
+            '{
+                "type": "object",
+                "properties": {
+                    "foo": { "required": true }
+                }
+            }'
+        ];
+        yield [
+            '{
+              "string":{}
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "string":{"type":"string", "required": true}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "number":{}
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "number":{"type":"number", "required": true}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "integer":{}
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "integer":{"type":"integer", "required": true}
+              }
+            }'
+        ];
+        yield [
+            '{
+                "boolean":{}
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "boolean":{"type":"boolean", "required": true}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "array":{}
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "array":{"type":"array", "required": true}
+              }
+            }',
+            Constraint::CHECK_MODE_NORMAL
+        ];
+        yield [
+            '{
+              "null":{}
+            }',
+            '{
+              "type":"object",
+              "properties": {
+                "null":{"type":"null", "required": true}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "foo": {"baz": 1.5}
+            }',
+            '{
+              "type": "object",
+              "properties": {
+                "foo": {
                   "type": "object",
                   "properties": {
-                    "foo": {
-                      "type": "object",
-                      "properties": {
-                        "bar": {"type": "number"}
-                      },
-                      "required": ["bar"]
-                    }
-                  }
-                }'
-            ],
-            [
-                '{
-                  "foo": {"baz": 1.5}
-                }',
-                '{
+                    "bar": {"type": "number"}
+                  },
+                  "required": ["bar"]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{
+              "foo": {"baz": 1.5}
+            }',
+            '{
+              "type": "object",
+              "properties": {
+                "foo": {
                   "type": "object",
                   "properties": {
-                    "foo": {
-                      "type": "object",
-                      "properties": {
-                        "bar": {"type": "number", "required": true}
-                      }
-                    }
+                    "bar": {"type": "number", "required": true}
                   }
-                }'
-            ],
+                }
+              }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "number": 1.4
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "number":{"type":"number","required":true}
-                  }
-                }'
-            ],
-            [
-                '{}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "number":{"type":"number"}
-                  }
-                }'
-            ],
-            [
-                '{}',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "number":{"type":"number","required":false}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "number": 0
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "number":{"type":"integer","required":true}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "is_active": false
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "is_active":{"type":"boolean","required":true}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "status": null
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "status":{"type":"null","required":true}
-                  }
-                }'
-            ],
-            [
-                '{
-                  "users": []
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "users":{"type":"array","required":true}
-                  }
-                }'
-            ],
-            [
-                '{
-                    "foo": "foo",
-                    "bar": 1.4
-                 }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "foo": {"type": "string", "required": true},
-                        "bar": {"type": "number"}
-                    },
-                    "required": ["bar"]
-                }'
-            ],
-            [
-                '{
-                    "foo": {"bar": 1.5}
-                }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "foo": {
-                            "type": "object",
-                            "properties": {
-                                "bar": {"type": "number"}
-                            },
-                            "required": ["bar"]
-                        }
-                    },
-                    "required": ["foo"]
-                }'
-            ],
-            [
-                '{
-                    "foo": {}
-                }',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "foo": { "required": true }
+        yield [
+            '{
+              "number": 1.4
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "number":{"type":"number","required":true}
+              }
+            }'
+        ];
+        yield [
+            '{}',
+            '{
+              "type":"object",
+              "properties":{
+                "number":{"type":"number"}
+              }
+            }'
+        ];
+        yield [
+            '{}',
+            '{
+              "type":"object",
+              "properties":{
+                "number":{"type":"number","required":false}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "number": 0
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "number":{"type":"integer","required":true}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "is_active": false
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "is_active":{"type":"boolean","required":true}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "status": null
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "status":{"type":"null","required":true}
+              }
+            }'
+        ];
+        yield [
+            '{
+              "users": []
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "users":{"type":"array","required":true}
+              }
+            }'
+        ];
+        yield [
+            '{
+                "foo": "foo",
+                "bar": 1.4
+             }',
+            '{
+                "type": "object",
+                "properties": {
+                    "foo": {"type": "string", "required": true},
+                    "bar": {"type": "number"}
+                },
+                "required": ["bar"]
+            }'
+        ];
+        yield [
+            '{
+                "foo": {"bar": 1.5}
+            }',
+            '{
+                "type": "object",
+                "properties": {
+                    "foo": {
+                        "type": "object",
+                        "properties": {
+                            "bar": {"type": "number"}
+                        },
+                        "required": ["bar"]
                     }
-                }'
-            ],
-            [
-                '{
-                  "boo": {"bar": 1.5}
-                }',
-                '{
+                },
+                "required": ["foo"]
+            }'
+        ];
+        yield [
+            '{
+                "foo": {}
+            }',
+            '{
+                "type": "object",
+                "properties": {
+                    "foo": { "required": true }
+                }
+            }'
+        ];
+        yield [
+            '{
+              "boo": {"bar": 1.5}
+            }',
+            '{
+              "type": "object",
+              "properties": {
+                "foo": {
                   "type": "object",
                   "properties": {
-                    "foo": {
-                      "type": "object",
-                      "properties": {
-                        "bar": {"type": "number"}
-                      },
-                      "required": ["bar"]
-                    }
-                  }
-                }'
-            ],
-            [
-                '{
-                  "boo": {"bar": 1.5}
-                }',
-                '{
+                    "bar": {"type": "number"}
+                  },
+                  "required": ["bar"]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{
+              "boo": {"bar": 1.5}
+            }',
+            '{
+              "type": "object",
+              "properties": {
+                "foo": {
                   "type": "object",
                   "properties": {
-                    "foo": {
-                      "type": "object",
-                      "properties": {
-                        "bar": {"type": "number", "required": true}
-                      }
-                    }
+                    "bar": {"type": "number", "required": true}
                   }
-                }'
-            ],
+                }
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/SchemaValidationTest.php b/tests/Constraints/SchemaValidationTest.php
index 65268f49..e7b41967 100644
--- a/tests/Constraints/SchemaValidationTest.php
+++ b/tests/Constraints/SchemaValidationTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -102,7 +97,7 @@ public function testValidCases($schema): void
 
     public function testNonObjectSchema(): void
     {
-        $this->expectException('\JsonSchema\Exception\RuntimeException');
+        $this->expectException(\JsonSchema\Exception\RuntimeException::class);
         $this->expectExceptionMessage('Cannot validate the schema of a non-object');
 
         $this->testValidCases('"notAnObject"');
@@ -110,7 +105,7 @@ public function testNonObjectSchema(): void
 
     public function testInvalidSchemaException(): void
     {
-        $this->expectException('\JsonSchema\Exception\InvalidSchemaException');
+        $this->expectException(\JsonSchema\Exception\InvalidSchemaException::class);
         $this->expectExceptionMessage('Schema did not pass validation');
 
         $input = json_decode('{}');
diff --git a/tests/Constraints/SelfDefinedSchemaTest.php b/tests/Constraints/SelfDefinedSchemaTest.php
index 4ac1b8a7..f23baa1c 100644
--- a/tests/Constraints/SelfDefinedSchemaTest.php
+++ b/tests/Constraints/SelfDefinedSchemaTest.php
@@ -1,80 +1,74 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
+use JsonSchema\Exception\InvalidArgumentException;
 use JsonSchema\Validator;
+use stdClass;
 
 class SelfDefinedSchemaTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                    "$schema": {
-                        "$schema": "http://json-schema.org/draft-04/schema#",
-                        "properties": {
-                            "name": {
-                                "type": "string"
-                            },
-                            "age" : {
-                                "type": "integer",
-                                "maximum": 25
-                            }
+        yield [
+            '{
+                "$schema": {
+                    "$schema": "http://json-schema.org/draft-04/schema#",
+                    "properties": {
+                        "name": {
+                            "type": "string"
+                        },
+                        "age" : {
+                            "type": "integer",
+                            "maximum": 25
                         }
-                    },
-                    "name" : "John Doe",
-                    "age" : 30,
-                    "type" : "object"
-                }',
-                ''
-            ]
+                    }
+                },
+                "name" : "John Doe",
+                "age" : 30,
+                "type" : "object"
+            }',
+            ''
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                    "$schema": {
-                        "$schema": "http://json-schema.org/draft-04/schema#",
-                        "properties": {
-                            "name": {
-                                "type": "string"
-                            },
-                            "age" : {
-                                "type": "integer",
-                                "maximum": 125
-                            }
+        yield [
+            '{
+                "$schema": {
+                    "$schema": "http://json-schema.org/draft-04/schema#",
+                    "properties": {
+                        "name": {
+                            "type": "string"
+                        },
+                        "age" : {
+                            "type": "integer",
+                            "maximum": 125
                         }
-                    },
-                    "name" : "John Doe",
-                    "age" : 30,
-                    "type" : "object"
-                }',
-                ''
-            ]
+                    }
+                },
+                "name" : "John Doe",
+                "age" : 30,
+                "type" : "object"
+            }',
+            ''
         ];
     }
 
     public function testInvalidArgumentException(): void
     {
-        $value = json_decode('{}');
-        $schema = json_decode('');
+        $value = new stdClass();
+        $schema = null;
 
         $v = new Validator();
 
-        $this->expectException('\JsonSchema\Exception\InvalidArgumentException');
+        $this->expectException(InvalidArgumentException::class);
 
         $v->validate($value, $schema);
     }
diff --git a/tests/Constraints/TupleTypingTest.php b/tests/Constraints/TupleTypingTest.php
index f565ae00..3c84c3d0 100644
--- a/tests/Constraints/TupleTypingTest.php
+++ b/tests/Constraints/TupleTypingTest.php
@@ -1,140 +1,132 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class TupleTypingTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "tupleTyping":[2,"a"]
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "tupleTyping":{
-                      "type":"array",
-                      "items":[
-                        {"type":"string"},
-                        {"type":"number"}
-                      ]
-                    }
-                  }
-                }'
-            ],
-            [
-                '{
-                  "tupleTyping":["2",2,true]
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "tupleTyping":{
-                      "type":"array",
-                      "items":[
-                        {"type":"string"},
-                        {"type":"number"}
-                      ] ,
-                      "additionalItems":false
-                    }
-                  }
-                }'
-            ],
-            [
-                '{
-                  "tupleTyping":["2",2,3]
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "tupleTyping":{
-                      "type":"array",
-                      "items":[
-                        {"type":"string"},
-                        {"type":"number"}
-                      ] ,
-                      "additionalItems":{"type":"string"}
-                    }
-                  }
-                }'
-            ],
-            [
-                '{"data": [1, "foo", true, 1.5]}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "data": {
-                            "type": "array",
-                            "items": [{}, {}, {}],
-                            "additionalItems": false
-                        }
+        yield [
+            '{
+              "tupleTyping":[2,"a"]
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "tupleTyping":{
+                  "type":"array",
+                  "items":[
+                    {"type":"string"},
+                    {"type":"number"}
+                  ]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{
+              "tupleTyping":["2",2,true]
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "tupleTyping":{
+                  "type":"array",
+                  "items":[
+                    {"type":"string"},
+                    {"type":"number"}
+                  ] ,
+                  "additionalItems":false
+                }
+              }
+            }'
+        ];
+        yield [
+            '{
+              "tupleTyping":["2",2,3]
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "tupleTyping":{
+                  "type":"array",
+                  "items":[
+                    {"type":"string"},
+                    {"type":"number"}
+                  ] ,
+                  "additionalItems":{"type":"string"}
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"data": [1, "foo", true, 1.5]}',
+            '{
+                "type": "object",
+                "properties": {
+                    "data": {
+                        "type": "array",
+                        "items": [{}, {}, {}],
+                        "additionalItems": false
                     }
-                }'
-            ]
+                }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "tupleTyping":["2", 1]
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "tupleTyping":{
-                      "type":"array",
-                      "items":[
-                        {"type":"string"},
-                        {"type":"number"}
-                      ]
-                    }
-                  }
-                }'
-            ],
-            [
-                '{
-                  "tupleTyping":["2",2,3]
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "tupleTyping":{
-                      "type":"array",
-                      "items":[
-                        {"type":"string"},
-                        {"type":"number"}
-                      ]
-                    }
-                  }
-                }'
-            ],
-            [
-                '{"data": [1, "foo", true]}',
-                '{
-                    "type": "object",
-                    "properties": {
-                        "data": {
-                            "type": "array",
-                            "items": [{}, {}, {}],
-                            "additionalItems": false
-                        }
+        yield [
+            '{
+              "tupleTyping":["2", 1]
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "tupleTyping":{
+                  "type":"array",
+                  "items":[
+                    {"type":"string"},
+                    {"type":"number"}
+                  ]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{
+              "tupleTyping":["2",2,3]
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "tupleTyping":{
+                  "type":"array",
+                  "items":[
+                    {"type":"string"},
+                    {"type":"number"}
+                  ]
+                }
+              }
+            }'
+        ];
+        yield [
+            '{"data": [1, "foo", true]}',
+            '{
+                "type": "object",
+                "properties": {
+                    "data": {
+                        "type": "array",
+                        "items": [{}, {}, {}],
+                        "additionalItems": false
                     }
-                }'
-            ]
+                }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/TypeTest.php b/tests/Constraints/TypeTest.php
index 1b6edc40..0aa830cb 100644
--- a/tests/Constraints/TypeTest.php
+++ b/tests/Constraints/TypeTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -13,13 +8,6 @@
 use JsonSchema\Constraints\TypeConstraint;
 use PHPUnit\Framework\TestCase;
 
-/**
- * Class TypeTest
- *
- * @package JsonSchema\Tests\Constraints
- *
- * @author hakre <https://github.com/hakre>
- */
 class TypeTest extends TestCase
 {
     /**
@@ -133,7 +121,7 @@ public function testValidateTypeException(): void
         $data = new \stdClass();
         $schema = json_decode('{"type": "notAValidTypeName"}');
 
-        $this->expectException('JsonSchema\Exception\InvalidArgumentException');
+        $this->expectException(\JsonSchema\Exception\InvalidArgumentException::class);
         $this->expectExceptionMessage('object is an invalid type for notAValidTypeName');
 
         $t->check($data, $schema);
diff --git a/tests/Constraints/UndefinedConstraintTest.php b/tests/Constraints/UndefinedConstraintTest.php
index 7e66a60b..d6fb2f2f 100644
--- a/tests/Constraints/UndefinedConstraintTest.php
+++ b/tests/Constraints/UndefinedConstraintTest.php
@@ -8,162 +8,134 @@
 
 class UndefinedConstraintTest extends BaseTestCase
 {
-    /**
-     * @return array{}
-     */
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [];
+        yield from [];
     }
 
-    /**
-     * @return array<string, array{input: string, schema: string, checkMode?: int}>
-     */
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            'oneOf with type coercion should not affect value passed to each sub schema (#790)' => [
-                'input' => <<<JSON
+        yield 'oneOf with type coercion should not affect value passed to each sub schema (#790)' => [
+            'input' => '{
+                "id": "LOC1",
+                "related_locations": [
                     {
-                        "id": "LOC1",
-                        "related_locations": [
-                            {
-                                "latitude": "51.047598",
-                                "longitude": "3.729943"
-                            }
-                        ]
+                        "latitude": "51.047598",
+                        "longitude": "3.729943"
                     }
-JSON
-                ,
-                'schema' => <<<JSON
-                    {
-                        "title": "Location",
-                        "type": "object",
-                        "properties": {
-                            "id": {
-                                "type": "string"
+                ]
+            }',
+            'schema' => '{
+                "title": "Location",
+                "type": "object",
+                "properties": {
+                    "id": {
+                        "type": "string"
+                    },
+                    "related_locations": {
+                        "oneOf": [
+                            {
+                                "type": "null"
                             },
-                            "related_locations": {
-                                "oneOf": [
-                                    {
-                                        "type": "null"
-                                    },
-                                    {
-                                        "type": "array",
-                                        "items": {
-                                            "type": "object",
-                                            "properties": {
-                                                "latitude": {
-                                                    "type": "string"
-                                                },
-                                                "longitude": {
-                                                    "type": "string"
-                                                }
-                                            }
+                            {
+                                "type": "array",
+                                "items": {
+                                    "type": "object",
+                                    "properties": {
+                                        "latitude": {
+                                            "type": "string"
+                                        },
+                                        "longitude": {
+                                            "type": "string"
                                         }
                                     }
-                                ]
+                                }
                             }
-                        }
+                        ]
                     }
-JSON
-                ,
-                'checkMode' => Constraint::CHECK_MODE_COERCE_TYPES
-            ],
-            'oneOf with apply defaults should not affect value passed to each sub schema (#510)' => [
-                'input' => <<<JSON
-                    {"foo": {"name": "bar"}}
-JSON
-                ,
-                'schema' => <<<JSON
+                }
+            }',
+            'checkMode' => Constraint::CHECK_MODE_COERCE_TYPES
+        ];
+        yield 'oneOf with apply defaults should not affect value passed to each sub schema (#510)' => [
+            'input' => '{"foo": {"name": "bar"}}',
+            'schema' => '{
+                "oneOf": [
                     {
-                        "oneOf": [
-                            {
+                        "type": "object",
+                        "properties": {
+                            "foo": {
                                 "type": "object",
                                 "properties": {
-                                    "foo": {
-                                        "type": "object",
-                                        "properties": {
-                                            "name": {"enum":["baz"],"default":"baz"},
-                                            "meta": {"enum":["baz"],"default":"baz"}
-                                        }
-                                    }
+                                    "name": {"enum":["baz"],"default":"baz"},
+                                    "meta": {"enum":["baz"],"default":"baz"}
                                 }
-                            },
-                            {
+                            }
+                        }
+                    },
+                    {
+                        "type": "object",
+                        "properties": {
+                            "foo": {
                                 "type": "object",
                                 "properties": {
-                                    "foo": {
-                                        "type": "object",
-                                        "properties": {
-                                            "name": {"enum":["bar"],"default":"bar"},
-                                            "meta": {"enum":["bar"],"default":"bar"}
-                                        }
-                                    }
+                                    "name": {"enum":["bar"],"default":"bar"},
+                                    "meta": {"enum":["bar"],"default":"bar"}
                                 }
-                            },
-                            {
+                            }
+                        }
+                    },
+                    {
+                        "type": "object",
+                        "properties": {
+                            "foo": {
                                 "type": "object",
                                 "properties": {
-                                    "foo": {
-                                        "type": "object",
-                                        "properties": {
-                                            "name": {"enum":["zip"],"default":"zip"},
-                                            "meta": {"enum":["zip"],"default":"zip"}
-                                        }
-                                    }
+                                    "name": {"enum":["zip"],"default":"zip"},
+                                    "meta": {"enum":["zip"],"default":"zip"}
                                 }
                             }
-                        ]
+                        }
                     }
-JSON
-                ,
-                'checkMode' => Constraint::CHECK_MODE_APPLY_DEFAULTS
-            ],
-            'anyOf with apply defaults should not affect value passed to each sub schema (#711)' => [
-                'input' => <<<JSON
-                    {
-                        "b": 2
+                ]
+            }',
+            'checkMode' => Constraint::CHECK_MODE_APPLY_DEFAULTS
+        ];
+        yield 'anyOf with apply defaults should not affect value passed to each sub schema (#711)' => [
+            'input' => '{ "b": 2 }',
+            'schema' => '{
+              "anyOf": [
+                {
+                  "required": [ "a" ],
+                  "pro": {
+                    "a": {
+                      "type": "integer"
+                    },
+                    "aDefault": {
+                      "type": "integer",
+                      "default": 1
                     }
-JSON
-                ,
-                'schema' => <<<JSON
-                    {
-                        "anyOf": [
-                            {
-                                "required": [ "a" ],
-                      "properties": {
-                          "a": {
-                              "type": "integer"
-                          },
-                          "aDefault": {
-                              "type": "integer",
-                              "default": 1
-                          }
-                      },
-                      "type": "object",
-                      "additionalProperties": false
+                  },
+                  "type": "object",
+                  "additionalProperties": false
+                },
+                {
+                  "required": [ "b" ],
+                  "properties": {
+                    "b": {
+                      "type": "integer"
                     },
-                    {
-                      "required": [ "b" ],
-                      "properties": {
-                          "b": {
-                              "type": "integer"
-                          },
-                          "bDefault": {
-                              "type": "integer",
-                              "default": 2
-                          }
-                      },
-                      "type": "object",
-                      "additionalProperties": false
+                    "bDefault": {
+                      "type": "integer",
+                      "default": 2
                     }
-                  ]
+                  },
+                  "type": "object",
+                  "additionalProperties": false
                 }
-JSON
-                ,
-                'checkMode' => Constraint::CHECK_MODE_APPLY_DEFAULTS
-            ]
+              ]
+            }',
+            'checkMode' => Constraint::CHECK_MODE_APPLY_DEFAULTS
         ];
     }
 }
diff --git a/tests/Constraints/UnionTypesTest.php b/tests/Constraints/UnionTypesTest.php
index 387848df..7dc87e71 100644
--- a/tests/Constraints/UnionTypesTest.php
+++ b/tests/Constraints/UnionTypesTest.php
@@ -1,53 +1,45 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class UnionTypesTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "stringOrNumber":4.8,
-                  "booleanOrNull":5
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "stringOrNumber":{"type":["string","number"]},
-                    "booleanOrNull":{"type":["boolean","null"]}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "stringOrNumber":4.8,
+              "booleanOrNull":5
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "stringOrNumber":{"type":["string","number"]},
+                "booleanOrNull":{"type":["boolean","null"]}
+              }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "stringOrNumber":4.8,
-                  "booleanOrNull":false
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "stringOrNumber":{"type":["string","number"]},
-                    "booleanOrNull":{"type":["boolean","null"]}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "stringOrNumber":4.8,
+              "booleanOrNull":false
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "stringOrNumber":{"type":["string","number"]},
+                "booleanOrNull":{"type":["boolean","null"]}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/UnionWithNullValueTest.php b/tests/Constraints/UnionWithNullValueTest.php
index 16d2d8b2..79709891 100644
--- a/tests/Constraints/UnionWithNullValueTest.php
+++ b/tests/Constraints/UnionWithNullValueTest.php
@@ -1,53 +1,45 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class UnionWithNullValueTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "stringOrNumber":null,
-                  "booleanOrNull":null
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "stringOrNumber":{"type":["string","number"]},
-                    "booleanOrNull":{"type":["boolean","null"]}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "stringOrNumber":null,
+              "booleanOrNull":null
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "stringOrNumber":{"type":["string","number"]},
+                "booleanOrNull":{"type":["boolean","null"]}
+              }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "stringOrNumber":12,
-                  "booleanOrNull":null
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "stringOrNumber":{"type":["string","number"]},
-                    "booleanOrNull":{"type":["boolean","null"]}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "stringOrNumber":12,
+              "booleanOrNull":null
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "stringOrNumber":{"type":["string","number"]},
+                "booleanOrNull":{"type":["boolean","null"]}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/UniqueItemsTest.php b/tests/Constraints/UniqueItemsTest.php
index 0badfe1d..e3e8e3c5 100644
--- a/tests/Constraints/UniqueItemsTest.php
+++ b/tests/Constraints/UniqueItemsTest.php
@@ -1,165 +1,157 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class UniqueItemsTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            'Non unique integers' => [
-                'input' => '[1,2,2]',
-                'schema' => '{
-                  "type":"array",
-                  "uniqueItems": true
-                }'
-            ],
-            'Non unique objects' => [
-                'input' => '[{"a":"b"},{"a":"c"},{"a":"b"}]',
-                'schema' => '{
-                  "type":"array",
-                  "uniqueItems": true
-                }'
-            ],
-            'Non unique objects - three levels deep' => [
-                'input' => '[{"foo": {"bar" : {"baz" : true}}}, {"foo": {"bar" : {"baz" : true}}}]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'Non unique mathematical values for the number one' => [
-                'input' => '[1.0, 1.00, 1]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'Non unique arrays' => [
-                'input' => '[["foo"], ["foo"]]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'Non unique mix of different types' => [
-                'input' => '[{}, [1], true, null, {}, 1]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'objects are non-unique despite key order' => [
-                'input' => '[{"a": 1, "b": 2}, {"b": 2, "a": 1}]',
-                'schema' => '{"uniqueItems": true}',
-            ]
+        yield 'Non unique integers' => [
+            'input' => '[1,2,2]',
+            'schema' => '{
+              "type":"array",
+              "uniqueItems": true
+            }'
+        ];
+        yield 'Non unique objects' => [
+            'input' => '[{"a":"b"},{"a":"c"},{"a":"b"}]',
+            'schema' => '{
+              "type":"array",
+              "uniqueItems": true
+            }'
+        ];
+        yield 'Non unique objects - three levels deep' => [
+            'input' => '[{"foo": {"bar" : {"baz" : true}}}, {"foo": {"bar" : {"baz" : true}}}]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'Non unique mathematical values for the number one' => [
+            'input' => '[1.0, 1.00, 1]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'Non unique arrays' => [
+            'input' => '[["foo"], ["foo"]]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'Non unique mix of different types' => [
+            'input' => '[{}, [1], true, null, {}, 1]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'objects are non-unique despite key order' => [
+            'input' => '[{"a": 1, "b": 2}, {"b": 2, "a": 1}]',
+            'schema' => '{"uniqueItems": true}',
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            'unique integers' => [
-                'input' => '[1,2,3]',
-                'schema' => '{
-                    "type":"array",
-                    "uniqueItems": true
-                }'
-            ],
-            'unique objects' =>[
-                'input' => '[{"foo": 12}, {"bar": false}]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'Integer one and boolean true' => [
-                'input' => '[1, true]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'Integer zero and boolean false' => [
-                'input' => '[0, false]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'Objects with different value three levels deep' => [
-                'input' => '[{"foo": {"bar" : {"baz" : true}}}, {"foo": {"bar" : {"baz" : false}}}]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'Array of strings' => [
-                'input' => '[["foo"], ["bar"]]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            'Object, Array, boolean, null and integer' => [
-                'input' => '[{}, [1], true, null, 1]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": true
-                }'
-            ],
-            // below equals the invalid tests, but with uniqueItems set to false
-            'Non unique integers' => [
-                'input' => '[1,2,2]',
-                'schema' =>  '{
-                  "type":"array",
-                  "uniqueItems": false
-                }'
-            ],
-            'Non unique objects' => [
-                'input' => '[{"a":"b"},{"a":"c"},{"a":"b"}]',
-                'schema' => '{
-                  "type":"array",
-                  "uniqueItems": false
-                }'
-            ],
-            'Non unique objects - three levels deep' => [
-                'input' => '[{"foo": {"bar" : {"baz" : true}}}, {"foo": {"bar" : {"baz" : true}}}]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": false
-                }'
-            ],
-            'Non unique mathematical values for the number one' => [
-                'input' => '[1.0, 1.00, 1]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": false
-                }'
-            ],
-            'Non unique arrays' => [
-                'input' => '[["foo"], ["foo"]]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": false
-                }'
-            ],
-            'Non unique mix of different types' => [
-                'input' => '[{}, [1], true, null, {}, 1]',
-                'schema' => '{
-                    "type": "array",
-                    "uniqueItems": false
-                }'
-            ]
+        yield 'unique integers' => [
+            'input' => '[1,2,3]',
+            'schema' => '{
+                "type":"array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'unique objects' =>[
+            'input' => '[{"foo": 12}, {"bar": false}]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'Integer one and boolean true' => [
+            'input' => '[1, true]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'Integer zero and boolean false' => [
+            'input' => '[0, false]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'Objects with different value three levels deep' => [
+            'input' => '[{"foo": {"bar" : {"baz" : true}}}, {"foo": {"bar" : {"baz" : false}}}]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'Array of strings' => [
+            'input' => '[["foo"], ["bar"]]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        yield 'Object, Array, boolean, null and integer' => [
+            'input' => '[{}, [1], true, null, 1]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": true
+            }'
+        ];
+        // below equals the invalid tests, but with uniqueItems set to false
+        yield 'Non unique integers' => [
+            'input' => '[1,2,2]',
+            'schema' =>  '{
+              "type":"array",
+              "uniqueItems": false
+            }'
+        ];
+        yield 'Non unique objects' => [
+            'input' => '[{"a":"b"},{"a":"c"},{"a":"b"}]',
+            'schema' => '{
+              "type":"array",
+              "uniqueItems": false
+            }'
+        ];
+        yield 'Non unique objects - three levels deep' => [
+            'input' => '[{"foo": {"bar" : {"baz" : true}}}, {"foo": {"bar" : {"baz" : true}}}]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": false
+            }'
+        ];
+        yield 'Non unique mathematical values for the number one' => [
+            'input' => '[1.0, 1.00, 1]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": false
+            }'
+        ];
+        yield 'Non unique arrays' => [
+            'input' => '[["foo"], ["foo"]]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": false
+            }'
+        ];
+        yield 'Non unique mix of different types' => [
+            'input' => '[{}, [1], true, null, {}, 1]',
+            'schema' => '{
+                "type": "array",
+                "uniqueItems": false
+            }'
         ];
     }
 }
diff --git a/tests/Constraints/ValidationExceptionTest.php b/tests/Constraints/ValidationExceptionTest.php
index ac6d973d..bb0fd162 100644
--- a/tests/Constraints/ValidationExceptionTest.php
+++ b/tests/Constraints/ValidationExceptionTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
@@ -19,7 +14,7 @@ class ValidationExceptionTest extends TestCase
     public function testValidationException(): void
     {
         $exception = new ValidationException();
-        $this->assertInstanceOf('\JsonSchema\Exception\ValidationException', $exception);
+        $this->assertInstanceOf(\JsonSchema\Exception\ValidationException::class, $exception);
 
         $checkValue = json_decode('{"propertyOne": "thisIsNotAnObject"}');
         $schema = json_decode('{
@@ -45,7 +40,7 @@ public function testValidationException(): void
             $exception->getMessage()
         );
 
-        $this->expectException('JsonSchema\Exception\ValidationException');
+        $this->expectException(\JsonSchema\Exception\ValidationException::class);
         throw $exception;
     }
 }
diff --git a/tests/Constraints/WrongMessagesFailingTestCaseTest.php b/tests/Constraints/WrongMessagesFailingTestCaseTest.php
index e36f57ce..6ed20e56 100644
--- a/tests/Constraints/WrongMessagesFailingTestCaseTest.php
+++ b/tests/Constraints/WrongMessagesFailingTestCaseTest.php
@@ -1,53 +1,45 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Constraints;
 
 class WrongMessagesFailingTestCaseTest extends BaseTestCase
 {
+    /** @var bool */
     protected $validateSchema = true;
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "stringOrNumber":4.8,
-                  "booleanOrNull":["A","B"]
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "stringOrNumber":{"type":["string","number"]},
-                    "booleanOrNull":{"type":["boolean","null"]}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "stringOrNumber":4.8,
+              "booleanOrNull":["A","B"]
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "stringOrNumber":{"type":["string","number"]},
+                "booleanOrNull":{"type":["boolean","null"]}
+              }
+            }'
         ];
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return [
-            [
-                '{
-                  "stringOrNumber":4.8,
-                  "booleanOrNull":true
-                }',
-                '{
-                  "type":"object",
-                  "properties":{
-                    "stringOrNumber":{"type":["string","number"]},
-                    "booleanOrNull":{"type":["boolean","null"]}
-                  }
-                }'
-            ]
+        yield [
+            '{
+              "stringOrNumber":4.8,
+              "booleanOrNull":true
+            }',
+            '{
+              "type":"object",
+              "properties":{
+                "stringOrNumber":{"type":["string","number"]},
+                "booleanOrNull":{"type":["boolean","null"]}
+              }
+            }'
         ];
     }
 }
diff --git a/tests/Drafts/BaseDraftTestCase.php b/tests/Drafts/BaseDraftTestCase.php
index 9a4d564f..f74bc85e 100644
--- a/tests/Drafts/BaseDraftTestCase.php
+++ b/tests/Drafts/BaseDraftTestCase.php
@@ -45,14 +45,14 @@ private function setUpTests(bool $isValid): array
         return $tests;
     }
 
-    public function getInvalidTests(): array
+    public function getInvalidTests(): \Generator
     {
-        return $this->setUpTests(false);
+        yield from $this->setUpTests(false);
     }
 
-    public function getValidTests(): array
+    public function getValidTests(): \Generator
     {
-        return $this->setUpTests(true);
+        yield from $this->setUpTests(true);
     }
 
     /**
diff --git a/tests/Drafts/Draft3Test.php b/tests/Drafts/Draft3Test.php
index bebc6eaf..4ed6f76c 100644
--- a/tests/Drafts/Draft3Test.php
+++ b/tests/Drafts/Draft3Test.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Drafts;
 
@@ -13,12 +8,11 @@
 use JsonSchema\SchemaStorage;
 use JsonSchema\Validator;
 
-/**
- * @package JsonSchema\Tests\Drafts
- */
 class Draft3Test extends BaseDraftTestCase
 {
+    /** @var string */
     protected $schemaSpec = 'http://json-schema.org/draft-03/schema#';
+    /** @var bool */
     protected $validateSchema = true;
 
     /**
@@ -81,26 +75,34 @@ protected function getFilePaths(): array
         ];
     }
 
-    public function getInvalidForAssocTests(): array
+    public function getInvalidForAssocTests(): \Generator
     {
-        $tests = parent::getInvalidForAssocTests();
-        unset(
-            $tests['type.json / object type matches objects / an array is not an object'],
-            $tests['type.json / array type matches arrays / an object is not an array']
-        );
+        $skip = [
+            'type.json / object type matches objects / an array is not an object',
+            'type.json / array type matches arrays / an object is not an array',
+        ];
 
-        return $tests;
+        foreach (parent::getInvalidForAssocTests() as $name => $testcase) {
+            if (in_array($name, $skip, true)) {
+                continue;
+            }
+            yield $name => $testcase;
+        }
     }
 
-    public function getValidForAssocTests(): array
+    public function getValidForAssocTests(): \Generator
     {
-        $tests = parent::getValidForAssocTests();
-        unset(
-            $tests['type.json / object type matches objects / an array is not an object'],
-            $tests['type.json / array type matches arrays / an object is not an array']
-        );
+        $skip = [
+            'type.json / object type matches objects / an array is not an object',
+            'type.json / array type matches arrays / an object is not an array',
+        ];
 
-        return $tests;
+        foreach (parent::getValidForAssocTests() as $name => $testcase) {
+            if (in_array($name, $skip, true)) {
+                continue;
+            }
+            yield $name => $testcase;
+        }
     }
 
     /**
diff --git a/tests/Drafts/Draft4Test.php b/tests/Drafts/Draft4Test.php
index 16c73b45..dbf1354a 100644
--- a/tests/Drafts/Draft4Test.php
+++ b/tests/Drafts/Draft4Test.php
@@ -1,17 +1,9 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Drafts;
 
-/**
- * @package JsonSchema\Tests\Drafts
- */
 class Draft4Test extends BaseDraftTestCase
 {
     /** @var bool */
@@ -28,26 +20,34 @@ protected function getFilePaths(): array
         ];
     }
 
-    public function getInvalidForAssocTests(): array
+    public function getInvalidForAssocTests(): \Generator
     {
-        $tests = parent::getInvalidForAssocTests();
-        unset(
-            $tests['type.json / object type matches objects / an array is not an object'],
-            $tests['type.json / array type matches arrays / an object is not an array']
-        );
+        $skip = [
+            'type.json / object type matches objects / an array is not an object',
+            'type.json / array type matches arrays / an object is not an array',
+        ];
 
-        return $tests;
+        foreach (parent::getInvalidForAssocTests() as $name => $testcase) {
+            if (in_array($name, $skip, true)) {
+                continue;
+            }
+            yield $name => $testcase;
+        }
     }
 
-    public function getValidForAssocTests(): array
+    public function getValidForAssocTests(): \Generator
     {
-        $tests = parent::getValidForAssocTests();
-        unset(
-            $tests['type.json / object type matches objects / an array is not an object'],
-            $tests['type.json / array type matches arrays / an object is not an array']
-        );
+        $skip = [
+            'type.json / object type matches objects / an array is not an object',
+            'type.json / array type matches arrays / an object is not an array',
+        ];
 
-        return $tests;
+        foreach (parent::getValidForAssocTests() as $name => $testcase) {
+            if (in_array($name, $skip, true)) {
+                continue;
+            }
+            yield $name => $testcase;
+        }
     }
 
     /**
diff --git a/tests/Entity/JsonPointerTest.php b/tests/Entity/JsonPointerTest.php
index cb27c68e..f6be6621 100644
--- a/tests/Entity/JsonPointerTest.php
+++ b/tests/Entity/JsonPointerTest.php
@@ -2,24 +2,12 @@
 
 declare(strict_types=1);
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
 namespace JsonSchema\Tests\Entity;
 
 use JsonSchema\Entity\JsonPointer;
 use JsonSchema\Exception\InvalidArgumentException;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @package JsonSchema\Tests\Entity
- *
- * @author Joost Nijhuis <jnijhuis81@gmail.com>
- */
 class JsonPointerTest extends TestCase
 {
     /**
diff --git a/tests/Exception/InvalidArgumentExceptionTest.php b/tests/Exception/InvalidArgumentExceptionTest.php
index 01243760..12b72a7a 100644
--- a/tests/Exception/InvalidArgumentExceptionTest.php
+++ b/tests/Exception/InvalidArgumentExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Exception;
 
 use JsonSchema\Exception\InvalidArgumentException;
@@ -11,6 +13,6 @@ public function testHierarchy(): void
     {
         $exception = new InvalidArgumentException();
         self::assertInstanceOf('\InvalidArgumentException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\ExceptionInterface', $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\ExceptionInterface::class, $exception);
     }
 }
diff --git a/tests/Exception/InvalidSchemaMediaTypeExceptionTest.php b/tests/Exception/InvalidSchemaMediaTypeExceptionTest.php
index c3930db9..0d85647b 100644
--- a/tests/Exception/InvalidSchemaMediaTypeExceptionTest.php
+++ b/tests/Exception/InvalidSchemaMediaTypeExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Exception;
 
 use JsonSchema\Exception\InvalidSchemaMediaTypeException;
@@ -11,7 +13,7 @@ public function testHierarchy(): void
     {
         $exception = new InvalidSchemaMediaTypeException();
         self::assertInstanceOf('\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\ExceptionInterface', $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\RuntimeException::class, $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\ExceptionInterface::class, $exception);
     }
 }
diff --git a/tests/Exception/InvalidSourceUriExceptionTest.php b/tests/Exception/InvalidSourceUriExceptionTest.php
index c7fd48bc..c302e82c 100644
--- a/tests/Exception/InvalidSourceUriExceptionTest.php
+++ b/tests/Exception/InvalidSourceUriExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Exception;
 
 use JsonSchema\Exception\InvalidSourceUriException;
@@ -11,7 +13,7 @@ public function testHierarchy(): void
     {
         $exception = new InvalidSourceUriException();
         self::assertInstanceOf('\InvalidArgumentException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\InvalidArgumentException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\ExceptionInterface', $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\InvalidArgumentException::class, $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\ExceptionInterface::class, $exception);
     }
 }
diff --git a/tests/Exception/JsonDecodingExceptionTest.php b/tests/Exception/JsonDecodingExceptionTest.php
index 468165e4..391c94d1 100644
--- a/tests/Exception/JsonDecodingExceptionTest.php
+++ b/tests/Exception/JsonDecodingExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Exception;
 
 use JsonSchema\Exception\JsonDecodingException;
@@ -11,8 +13,8 @@ public function testHierarchy(): void
     {
         $exception = new JsonDecodingException();
         self::assertInstanceOf('\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\ExceptionInterface', $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\RuntimeException::class, $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\ExceptionInterface::class, $exception);
     }
 
     public function testDefaultMessage()
diff --git a/tests/Exception/ResourceNotFoundExceptionTest.php b/tests/Exception/ResourceNotFoundExceptionTest.php
index fe87575c..d225b0dd 100644
--- a/tests/Exception/ResourceNotFoundExceptionTest.php
+++ b/tests/Exception/ResourceNotFoundExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Exception;
 
 use JsonSchema\Exception\ResourceNotFoundException;
@@ -11,7 +13,7 @@ public function testHierarchy(): void
     {
         $exception = new ResourceNotFoundException();
         self::assertInstanceOf('\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\ExceptionInterface', $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\RuntimeException::class, $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\ExceptionInterface::class, $exception);
     }
 }
diff --git a/tests/Exception/RuntimeExceptionTest.php b/tests/Exception/RuntimeExceptionTest.php
index cf34439b..a30fa527 100644
--- a/tests/Exception/RuntimeExceptionTest.php
+++ b/tests/Exception/RuntimeExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Exception;
 
 use JsonSchema\Exception\RuntimeException;
@@ -11,6 +13,6 @@ public function testHierarchy(): void
     {
         $exception = new RuntimeException();
         self::assertInstanceOf('\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\ExceptionInterface', $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\ExceptionInterface::class, $exception);
     }
 }
diff --git a/tests/Exception/UnresolvableJsonPointerExceptionTest.php b/tests/Exception/UnresolvableJsonPointerExceptionTest.php
index 5255c5c5..68500b86 100644
--- a/tests/Exception/UnresolvableJsonPointerExceptionTest.php
+++ b/tests/Exception/UnresolvableJsonPointerExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Exception;
 
 use JsonSchema\Exception\UnresolvableJsonPointerException;
@@ -11,7 +13,7 @@ public function testHierarchy(): void
     {
         $exception = new UnresolvableJsonPointerException();
         self::assertInstanceOf('\InvalidArgumentException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\InvalidArgumentException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\ExceptionInterface', $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\InvalidArgumentException::class, $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\ExceptionInterface::class, $exception);
     }
 }
diff --git a/tests/Exception/UriResolverExceptionTest.php b/tests/Exception/UriResolverExceptionTest.php
index 630f30a2..0aaf01f4 100644
--- a/tests/Exception/UriResolverExceptionTest.php
+++ b/tests/Exception/UriResolverExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Exception;
 
 use JsonSchema\Exception\UriResolverException;
@@ -11,7 +13,7 @@ public function testHierarchy(): void
     {
         $exception = new UriResolverException();
         self::assertInstanceOf('\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\RuntimeException', $exception);
-        self::assertInstanceOf('\JsonSchema\Exception\ExceptionInterface', $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\RuntimeException::class, $exception);
+        self::assertInstanceOf(\JsonSchema\Exception\ExceptionInterface::class, $exception);
     }
 }
diff --git a/tests/Iterators/ObjectIteratorTest.php b/tests/Iterators/ObjectIteratorTest.php
index 258a0156..8ee33fe4 100644
--- a/tests/Iterators/ObjectIteratorTest.php
+++ b/tests/Iterators/ObjectIteratorTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Iterators;
 
@@ -39,7 +34,7 @@ public function testCreate(): void
     {
         $i = new ObjectIterator($this->testObject);
 
-        $this->assertInstanceOf('\JsonSchema\Iterator\ObjectIterator', $i);
+        $this->assertInstanceOf(\JsonSchema\Iterator\ObjectIterator::class, $i);
     }
 
     public function testInitialState(): void
diff --git a/tests/RefTest.php b/tests/RefTest.php
index 3b66d586..574fe9ca 100644
--- a/tests/RefTest.php
+++ b/tests/RefTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests;
 
@@ -56,7 +51,7 @@ public function dataRefIgnoresSiblings(): array
                 }',
                 '{"propertyOne": 5}',
                 true,
-                '\JsonSchema\Exception\UnresolvableJsonPointerException'
+                \JsonSchema\Exception\UnresolvableJsonPointerException::class
             ]
         ];
     }
diff --git a/tests/SchemaStorageTest.php b/tests/SchemaStorageTest.php
index 812fe804..502a5821 100644
--- a/tests/SchemaStorageTest.php
+++ b/tests/SchemaStorageTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests;
 
@@ -21,7 +16,7 @@ public function testResolveRef(): void
         $mainSchema = $this->getMainSchema();
         $mainSchemaPath = 'http://www.example.com/schema.json';
 
-        $uriRetriever = $this->prophesize('JsonSchema\UriRetrieverInterface');
+        $uriRetriever = $this->prophesize(\JsonSchema\UriRetrieverInterface::class);
         $uriRetriever->retrieve($mainSchemaPath)->willReturn($mainSchema)->shouldBeCalled();
 
         $schemaStorage = new SchemaStorage($uriRetriever->reveal());
@@ -55,7 +50,7 @@ public function testSchemaWithLocalAndExternalReferencesWithCircularReference():
         $schema3Path = 'http://www.my-domain.com/schema3.json';
 
         /** @var UriRetriever $uriRetriever */
-        $uriRetriever = $this->prophesize('JsonSchema\UriRetrieverInterface');
+        $uriRetriever = $this->prophesize(\JsonSchema\UriRetrieverInterface::class);
         $uriRetriever->retrieve($mainSchemaPath)->willReturn($mainSchema)->shouldBeCalled();
         $uriRetriever->retrieve($schema2Path)->willReturn($schema2)->shouldBeCalled();
         $uriRetriever->retrieve($schema3Path)->willReturn($schema3)->shouldBeCalled();
@@ -102,13 +97,13 @@ public function testSchemaWithLocalAndExternalReferencesWithCircularReference():
 
     public function testUnresolvableJsonPointExceptionShouldBeThrown(): void
     {
-        $this->expectException('JsonSchema\Exception\UnresolvableJsonPointerException');
+        $this->expectException(\JsonSchema\Exception\UnresolvableJsonPointerException::class);
         $this->expectExceptionMessage('File: http://www.example.com/schema.json is found, but could not resolve fragment: #/definitions/car');
 
         $mainSchema = $this->getInvalidSchema();
         $mainSchemaPath = 'http://www.example.com/schema.json';
 
-        $uriRetriever = $this->prophesize('JsonSchema\UriRetrieverInterface');
+        $uriRetriever = $this->prophesize(\JsonSchema\UriRetrieverInterface::class);
         $uriRetriever->retrieve($mainSchemaPath)
             ->willReturn($mainSchema)
             ->shouldBeCalled();
@@ -119,7 +114,7 @@ public function testUnresolvableJsonPointExceptionShouldBeThrown(): void
 
     public function testResolveRefWithNoAssociatedFileName(): void
     {
-        $this->expectException('JsonSchema\Exception\UnresolvableJsonPointerException');
+        $this->expectException(\JsonSchema\Exception\UnresolvableJsonPointerException::class);
         $this->expectExceptionMessage("Could not resolve fragment '#': no file is defined");
 
         $schemaStorage = new SchemaStorage();
@@ -264,14 +259,14 @@ public function testGetUriRetriever(): void
     {
         $s = new SchemaStorage();
         $s->addSchema('http://json-schema.org/draft-04/schema#');
-        $this->assertInstanceOf('\JsonSchema\Uri\UriRetriever', $s->getUriRetriever());
+        $this->assertInstanceOf(\JsonSchema\Uri\UriRetriever::class, $s->getUriRetriever());
     }
 
     public function testGetUriResolver(): void
     {
         $s = new SchemaStorage();
         $s->addSchema('http://json-schema.org/draft-04/schema#');
-        $this->assertInstanceOf('\JsonSchema\Uri\UriResolver', $s->getUriResolver());
+        $this->assertInstanceOf(\JsonSchema\Uri\UriResolver::class, $s->getUriResolver());
     }
 
     public function testMetaSchemaFixes(): void
@@ -291,7 +286,7 @@ public function testNoDoubleResolve(): void
     {
         $schemaOne = json_decode('{"id": "test/schema", "$ref": "../test2/schema2"}');
 
-        $uriRetriever = $this->prophesize('JsonSchema\UriRetrieverInterface');
+        $uriRetriever = $this->prophesize(\JsonSchema\UriRetrieverInterface::class);
         $uriRetriever->retrieve('test/schema')->willReturn($schemaOne)->shouldBeCalled();
 
         $s = new SchemaStorage($uriRetriever->reveal());
diff --git a/tests/Uri/Retrievers/CurlTest.php b/tests/Uri/Retrievers/CurlTest.php
index 5715773d..c2c88067 100644
--- a/tests/Uri/Retrievers/CurlTest.php
+++ b/tests/Uri/Retrievers/CurlTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Uri\Retrievers
 {
     use JsonSchema\Uri\Retrievers\Curl;
@@ -19,7 +21,7 @@ public function testRetrieveNonexistantFile(): void
         {
             $c = new Curl();
 
-            $this->expectException('\JsonSchema\Exception\ResourceNotFoundException');
+            $this->expectException(\JsonSchema\Exception\ResourceNotFoundException::class);
             $this->expectExceptionMessage('JSON schema not found');
 
             $c->retrieve(__DIR__ . '/notARealFile');
diff --git a/tests/Uri/Retrievers/FileGetContentsTest.php b/tests/Uri/Retrievers/FileGetContentsTest.php
index 57e6c90a..d48d7945 100644
--- a/tests/Uri/Retrievers/FileGetContentsTest.php
+++ b/tests/Uri/Retrievers/FileGetContentsTest.php
@@ -1,13 +1,12 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Uri\Retrievers;
 
 use JsonSchema\Uri\Retrievers\FileGetContents;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @group FileGetContents
- */
 class FileGetContentsTest extends TestCase
 {
     public function testFetchMissingFile(): void
diff --git a/tests/Uri/Retrievers/PredefinedArrayTest.php b/tests/Uri/Retrievers/PredefinedArrayTest.php
index c5436506..5594abfd 100644
--- a/tests/Uri/Retrievers/PredefinedArrayTest.php
+++ b/tests/Uri/Retrievers/PredefinedArrayTest.php
@@ -1,13 +1,12 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Uri\Retrievers;
 
 use JsonSchema\Uri\Retrievers\PredefinedArray;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @group PredefinedArray
- */
 class PredefinedArrayTest extends TestCase
 {
     private $retriever;
diff --git a/tests/Uri/UriResolverTest.php b/tests/Uri/UriResolverTest.php
index 8d524ca5..91dee39f 100644
--- a/tests/Uri/UriResolverTest.php
+++ b/tests/Uri/UriResolverTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests\Uri;
 
 use JsonSchema\Uri\UriResolver;
diff --git a/tests/Uri/UriRetrieverTest.php b/tests/Uri/UriRetrieverTest.php
index 81419269..0016cc4a 100644
--- a/tests/Uri/UriRetrieverTest.php
+++ b/tests/Uri/UriRetrieverTest.php
@@ -1,11 +1,6 @@
 <?php
 
-/*
- * This file is part of the JsonSchema package.
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
+declare(strict_types=1);
 
 namespace JsonSchema\Tests\Uri;
 
@@ -17,9 +12,6 @@
 use JsonSchema\Validator;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @group UriRetriever
- */
 class UriRetrieverTest extends TestCase
 {
     protected $validator;
@@ -37,7 +29,7 @@ private function getRetrieverMock($returnSchema)
             throw new JsonDecodingException($error);
         }
 
-        $retriever = $this->createMock('JsonSchema\Uri\UriRetriever');
+        $retriever = $this->createMock(\JsonSchema\Uri\UriRetriever::class);
 
         $retriever->expects($this->at(0))
                   ->method('retrieve')
@@ -235,7 +227,7 @@ public function testResolveExcessLevelUp(): void
 
     public function testConfirmMediaTypeAcceptsJsonSchemaType(): void
     {
-        $uriRetriever = $this->createMock('JsonSchema\Uri\Retrievers\UriRetrieverInterface');
+        $uriRetriever = $this->createMock(\JsonSchema\Uri\Retrievers\UriRetrieverInterface::class);
         $retriever = new UriRetriever();
 
         $uriRetriever->expects($this->at(0))
@@ -247,7 +239,7 @@ public function testConfirmMediaTypeAcceptsJsonSchemaType(): void
 
     public function testConfirmMediaTypeAcceptsJsonType(): void
     {
-        $uriRetriever = $this->createMock('JsonSchema\Uri\Retrievers\UriRetrieverInterface');
+        $uriRetriever = $this->createMock(\JsonSchema\Uri\Retrievers\UriRetrieverInterface::class);
         $retriever = new UriRetriever();
 
         $uriRetriever->expects($this->at(0))
@@ -259,7 +251,7 @@ public function testConfirmMediaTypeAcceptsJsonType(): void
 
     public function testConfirmMediaTypeThrowsExceptionForUnsupportedTypes(): void
     {
-        $uriRetriever = $this->createMock('JsonSchema\Uri\Retrievers\UriRetrieverInterface');
+        $uriRetriever = $this->createMock(\JsonSchema\Uri\Retrievers\UriRetrieverInterface::class);
         $retriever = new UriRetriever();
         $uriRetriever->expects($this->at(0))
                 ->method('getContentType')
@@ -274,11 +266,11 @@ private function mockRetriever($schema): void
     {
         $retrieverMock = $this->getRetrieverMock($schema);
 
-        $factory = new \ReflectionProperty('JsonSchema\Constraints\BaseConstraint', 'factory');
+        $factory = new \ReflectionProperty(\JsonSchema\Constraints\BaseConstraint::class, 'factory');
         $factory->setAccessible(true);
         $factory = $factory->getValue($this->validator);
 
-        $retriever = new \ReflectionProperty('JsonSchema\Constraints\Factory', 'uriRetriever');
+        $retriever = new \ReflectionProperty(\JsonSchema\Constraints\Factory::class, 'uriRetriever');
         $retriever->setAccessible(true);
         $retriever->setValue($factory, $retrieverMock);
     }
@@ -333,7 +325,7 @@ public function testRetrieveSchemaFromPackage(): void
 
     public function testInvalidContentTypeEndpointsDefault(): void
     {
-        $mock = $this->createMock('JsonSchema\Uri\Retrievers\UriRetrieverInterface');
+        $mock = $this->createMock(\JsonSchema\Uri\Retrievers\UriRetrieverInterface::class);
         $mock->method('getContentType')->willReturn('Application/X-Fake-Type');
         $retriever = new UriRetriever();
 
@@ -343,7 +335,7 @@ public function testInvalidContentTypeEndpointsDefault(): void
 
     public function testInvalidContentTypeEndpointsUnknown(): void
     {
-        $mock = $this->createMock('JsonSchema\Uri\Retrievers\UriRetrieverInterface');
+        $mock = $this->createMock(\JsonSchema\Uri\Retrievers\UriRetrieverInterface::class);
         $mock->method('getContentType')->willReturn('Application/X-Fake-Type');
         $retriever = new UriRetriever();
 
@@ -353,7 +345,7 @@ public function testInvalidContentTypeEndpointsUnknown(): void
 
     public function testInvalidContentTypeEndpointsAdded(): void
     {
-        $mock = $this->createMock('JsonSchema\Uri\Retrievers\UriRetrieverInterface');
+        $mock = $this->createMock(\JsonSchema\Uri\Retrievers\UriRetrieverInterface::class);
         $mock->method('getContentType')->willReturn('Application/X-Fake-Type');
         $retriever = new UriRetriever();
         $retriever->addInvalidContentTypeEndpoint('http://example.com');
@@ -386,7 +378,7 @@ public function testLoadSchemaJSONDecodingException(): void
     {
         $retriever = new UriRetriever();
 
-        $this->expectException('JsonSchema\Exception\JsonDecodingException');
+        $this->expectException(\JsonSchema\Exception\JsonDecodingException::class);
         $this->expectExceptionMessage('JSON syntax is malformed');
 
         $retriever->retrieve('package://tests/fixtures/bad-syntax.json');
diff --git a/tests/ValidatorTest.php b/tests/ValidatorTest.php
index 06eabc89..6c4d13af 100644
--- a/tests/ValidatorTest.php
+++ b/tests/ValidatorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace JsonSchema\Tests;
 
 use JsonSchema\Exception\InvalidArgumentException;