Setting some guidelines for testing

[hugofluhr]

Hi,

I think it would be nice to have some guidelines for writing test functions. For example, I am thinking that we could decide on where to use equality or all_close tests.

Maybe we can come up with some rules and put them somewhere in the documentation.

[smoia]

That is completely true - I don't have a good example nor idea in mind though. We can record what we're doing and how we're adjusting stuff in documentations - but we can also keep this issue in order to record questions and answers and decisions!

[mscheltienne]

Feel free to ping me on github on a PR with questions about testing/testing design choices.