Add Environment Wrapper Tests

[michele-milesi]

It would be nice to add a test for the environment wrappers we have. Maybe, using the dummy envs, we could do a couple of iterations and check that the obs/action matches those defined by the observation/action space.

@belerico, @DavideTr8: What do you think?

[belerico]

LGTM!

[DavideTr8]

Unittests are never enough

[belerico]

We can also test the environments without creating the expensive game underneath them by mocking the game creation and testing everything else