Make Assert\Assertion::stringify() UTF-8 safe.

Author: rquadling

lib/Assert/Assertion.php

@@ -2768,8 +2768,8 @@ protected static function stringify($value): string
         } elseif (\is_scalar($value)) {
             $val = (string)$value;
 
-            if (\strlen($val) > 100) {
-                $val = \substr($val, 0, 97).'...';
+            if (\mb_strlen($val) > 100) {
+                $val = \mb_substr($val, 0, 97).'...';
             }
 
             $result = $val;

tests/Assert/Tests/AssertTest.php

@@ -2103,6 +2103,18 @@ public function testStringifyTruncatesStringValuesLongerThan100CharactersAppropr
         $this->assertTrue(Assertion::float($string));
     }
 
+    /**
+     * @expectedException \Assert\AssertionFailedException
+     * @expectedExceptionCode \Assert\Assertion::INVALID_FLOAT
+     * @expectedExceptionMessage ငါကနံပါတ်မဟုတ်ဘူးငါကနံပါတ်မဟုတ်ဘူးငါကနံပါတ်မဟုတ်ဘူးငါကနံပါတ်မဟုတ်ဘူးငါကနံပါတ်မဟုတ်ဘူးငါကနံပါတ်မဟု...
+     */
+    public function testStringifyTruncatesStringValuesLongerThan100CharactersAppropriatelyAndIsMultibyteValid()
+    {
+        $string = str_repeat('ငါကနံပါတ်မဟုတ်ဘူး', 11);
+
+        $this->assertTrue(Assertion::float($string));
+    }
+
     /**
      * @expectedException \Assert\AssertionFailedException
      * @expectedExceptionCode \Assert\Assertion::INVALID_FLOAT