Checking that remote tests actually do something #595
Description
There were a few issues recently that pointed out that some of the modules has only mock test coverage and/or that some of the current tests don't really do anything (#594, #545 (comment)).
Going trough the modules and checking their tests may be a good task for a sprint.
Edit: I remove the module list from below, and would suggest to rather open separate, specific issues when we identify a module that is lacking such remote coverage.
This issue should then be closed when we come up with a way either to do this automatically either as a shell script-based hack or properly with upstream changes (e.g. astropy/pytest-remotedata#43).