PDOException：使用phpunit时找不到驱动程序

I am starting to use laravel 4 and I am trying to start using unit tests so I can make my live easier. Well as all of you will guess my development hasn't become easier after trying phpunit tests. The simple tests are well, easy but when the things start to get a bit more complicated they does not go as I though they will. I am starting to use laravel 4 and I am trying