Remove the `nottest` decorator from `tests/__init__.py` (see https://stackoverflow.com/questions/50610557/how-to-mark-one-function-not-a-test-for-pytest). I thought this decorator was needed in order to have helper functions in tests, but it turns out it is sufficient to make sure that functions are not named `test_...` if they are not tests. Resolve this issue after other test related issues, to easily make sure we do not break anything #7 #6 #5