Unit and Integration Testing

[CCInc]

Issue for tracking how to incorporate testing within the repo.

Unit testing

• [x] Ensure datasets remain downloadable and usable
• [x] Ensure datasets are loaded in the correct torch_geometric.data.Data format
• [x] Unit testing for custom transforms
• [x] Test that models get built correctly. Some good examples from PyG repository.

Integration testing

• [x] Test data->model pipeline end-to-end for combinations of datasets and models