I've added test functions for the index_functions/support.py module. Some comments:
I've started adding tests for index_functions/index_functions.py but want some feedback before I get ahead of myself. Do the test approach seem ok this far? An alternative would be to work with test-classes instead of test-functions, the iris project seems to do that. Do you have any preference either way?
Also, I'll add an issue for this merge before un-drafting it.