Symfony2 Testing Environment, disable functions

I wrote a new web application and everything works as it should, but we are going to test it with a few guys. So my question is, is there a way where we can write a testing environment or a testing file. The reason why we don't want to have some symfony functions enabled while in test mode ( Like Swift mailer, php curl and a few more ).

Do you guys have any idea how I can create this or what kind of approach shall I use to have this.

If you can provide a small example i will be grateful

Thanks in advance