PHPUnit_Framework_Assert::assertAttributeInternalType PHP Method

    public static function assertAttributeInternalType($expected, $attributeName, $classOrObject, $message = '')
    {
        static::assertInternalType($expected, static::readAttribute($classOrObject, $attributeName), $message);
    }

 /**
  * @Given /^the response json's "([^"]*)" key should be of type "([^"]*)"$/
  */
 public function theResponseJsonSKeyShouldBeOfType($keyword, $expectedType)
 {
     Assertions::assertAttributeInternalType($expectedType, $keyword, (object) $this->getResponse()->json());
 }