Test output shapes with PyTest

[omar-abdelgawad]

Is your feature request related to a problem? Please describe.
Currently, some modules (.py files) which are not supposed to be run have a main function as a kind of sanity check for the person writing the nn.Module or whatever. Most commonly we check for the input and output Tensor shapes to make sure the dims are correct. For example we might check that the output of a Generator should have the same size as its input with the same number of channels.

Describe the solution you'd like
All of the above sanity checks should be written separately with pytest.

Additional context
Please write tests that make sure the shapes of output torch.Tensors are correct after going through the generator or discriminator.