Tests cleaning & simplification (#81)

CONTRIBUTING.md

@@ -65,6 +65,26 @@ A good feature request addresses the following points:
 If your issue is well written we're already 80% of the way there by the time you
 post it.
 
+## Adding new policies, datasets or environments
+
+Look at our implementations for [datasets](./lerobot/common/datasets/), [policies](./lerobot/common/policies/),
+environments ([aloha](https://github.com/huggingface/gym-aloha),
+[xarm](https://github.com/huggingface/gym-xarm),
+[pusht](https://github.com/huggingface/gym-pusht))
+and follow the same api design.
+
+When implementing a new dataset class (e.g. `AlohaDataset`) follow these steps:
+- Update `available_datasets` in `lerobot/__init__.py`
+- Copy it in the required `available_datasets` class attribute
+
+When implementing a new environment (e.g. `gym_aloha`), follow these steps:
+- Update `available_envs`, `available_tasks_per_env` and `available_datasets` in `lerobot/__init__.py`
+
+When implementing a new policy class (e.g. `DiffusionPolicy`) follow these steps:
+- Update `available_policies` in `lerobot/__init__.py`
+- Set the required `name` class attribute.
+- Update variables in `tests/test_available.py` by importing your new Policy class
+
 ## Submitting a pull request (PR)
 
 Before writing code, we strongly advise you to search through the existing PRs or