We should have a test_requires

[jbrockmendel]

#18349 (comment)

we should have a test_requires, but that's separate. can you open an issue for that.

[jbrockmendel]

@jreback not sure how to make this actionable? Still needed?

[jreback]

i think can add to setup.py ?

[jbrockmendel]

Pretty sure that was the original idea, but no idea what was supposed to go in it.