Test class for container

[flip111]

The best Test baseclass to work with the container is WebTestCase.

However calling $this->getKernel() just returns null. Expected here either get the kernel or throw an exception.

Then to create the kernel the only option is to do $this->createClient() which gets a client which is useless if you just want the kernel.

Last a convenience function to access the container would be nice, perhaps ->get() like in symfony controllers to get services.