private function generateHash($migrations, $fixtures)
    {
        if ($migrations) {
            array_walk($migrations, function (& $migration) {
                $migration .= '@' . filemtime($migration);
            });
        }

        $classNames = array_map('get_class', $fixtures);

        foreach ($classNames as & $className) {
            $class    = new \ReflectionClass($className);
            $fileName = $class->getFileName();

            $className .= ':' . $fileName . '@' . filemtime($fileName);
        }

        sort($classNames);

        return sha1(serialize(array($migrations, $classNames)));
    }