Remove extra cache clear statement in tests.

tests/ModelTestCase.php

@@ -50,9 +50,6 @@ abstract class ModelTestCase extends \PHPUnit_Extensions_Database_TestCase
             $this->connection = $this->createDefaultDBConnection(self::$pdo, getenv('DB_NAME'));
         }
 
-        // It is important to clear the cache of the entity manager every time a new test runs!
-        self::$em->clear();
-
         return $this->connection;
     }