Improve failure message for assertIsList()

Author: sebastianbergmann

src/Framework/Constraint/Traversable/IsList.php

@@ -10,7 +10,9 @@
 namespace PHPUnit\Framework\Constraint;
 
 use function array_is_list;
+use function gettype;
 use function is_array;
+use function strtolower;
 
 /**
  * @no-named-arguments Parameter names are not covered by the backward compatibility promise for PHPUnit
@@ -22,7 +24,7 @@ final class IsList extends Constraint
      */
     public function toString(): string
     {
-        return 'is list';
+        return 'is a list';
     }
 
     /**
@@ -46,6 +48,20 @@ protected function matches(mixed $other): bool
      */
     protected function failureDescription(mixed $other): string
     {
-        return 'an array ' . $this->toString();
+        $type = strtolower(gettype($other));
+
+        if ($type === 'double') {
+            $type = 'float';
+        }
+
+        if ($type === 'resource (closed)') {
+            $type = 'closed resource';
+        }
+
+        return match ($type) {
+            'array', 'integer', 'object' => 'an ' . $type . ' ' . $this->toString(),
+            'boolean', 'float', 'null', 'resource', 'string' => 'a ' . $type . ' ' . $this->toString(),
+            default => 'a value of ' . $type . ' ' . $this->toString(),
+        };
     }
 }

tests/unit/Framework/Constraint/IsListTest.php

@@ -31,15 +31,15 @@ public function testConstraintIsNotList(): void
         $constraint = new IsList;
 
         $this->assertFalse($constraint->evaluate([1 => 1], '', true));
-        $this->assertEquals('is list', $constraint->toString());
+        $this->assertEquals('is a list', $constraint->toString());
         $this->assertCount(1, $constraint);
 
         try {
             $constraint->evaluate([1 => 1]);
         } catch (ExpectationFailedException $e) {
             $this->assertEquals(
                 <<<'EOF'
-Failed asserting that an array is list.
+Failed asserting that an array is a list.
 
 EOF
                 ,
@@ -57,15 +57,15 @@ public function testConstraintIsNotListWithFilteredArray(): void
         $constraint = new IsList;
 
         $this->assertFalse($constraint->evaluate([0 => 0, 1 => 1, 3 => 3], '', true));
-        $this->assertEquals('is list', $constraint->toString());
+        $this->assertEquals('is a list', $constraint->toString());
         $this->assertCount(1, $constraint);
 
         try {
             $constraint->evaluate([1 => 1]);
         } catch (ExpectationFailedException $e) {
             $this->assertEquals(
                 <<<'EOF'
-Failed asserting that an array is list.
+Failed asserting that an array is a list.
 
 EOF
                 ,
@@ -88,7 +88,7 @@ public function testConstraintIsNotListWithCustomMessage(): void
             $this->assertEquals(
                 <<<'EOF'
 custom message
-Failed asserting that an array is list.
+Failed asserting that an array is a list.
 
 EOF
                 ,
@@ -110,7 +110,7 @@ public function testConstraintIsNotListWhenNotArray(): void
         } catch (ExpectationFailedException $e) {
             $this->assertEquals(
                 <<<'EOF'
-Failed asserting that an array is list.
+Failed asserting that a string is a list.
 
 EOF
                 ,
@@ -131,7 +131,7 @@ public function testConstraintArrayIsNotList(): void
             $this->assertEquals(
                 <<<'EOF'
 custom message
-Failed asserting that an array is not list.
+Failed asserting that an array is not a list.
 
 EOF
                 ,