replace assertEmpty() with stricter assertions

Author: xabbuh

Tests/Validator/DoctrineLoaderTest.php

@@ -210,7 +210,7 @@ public function testClassNoAutoMapping()
         $this->assertSame(AutoMappingStrategy::DISABLED, $classMetadata->getAutoMappingStrategy());
 
         $maxLengthMetadata = $classMetadata->getPropertyMetadata('maxLength');
-        $this->assertEmpty($maxLengthMetadata);
+        $this->assertSame([], $maxLengthMetadata);
 
         /** @var PropertyMetadata[] $autoMappingExplicitlyEnabledMetadata */
         $autoMappingExplicitlyEnabledMetadata = $classMetadata->getPropertyMetadata('autoMappingExplicitlyEnabled');