Code Coverage on Testing

[GHLgh]

I think we should have code coverage for testing to make sure unit tests cover everything.

This is the library I found and we can see how to incorporate it into our tests.

And related stackoverflow post:
http://stackoverflow.com/questions/34728734/python-unit-test-coverage

[danyaljj]

Not sure how useful their result is though.
It would certainly tell us how much we are covering
But often it is unclear how to interpret their numbers.
I would rather we continue the current trend of incrementally adding the tests, whenever any issue comes up.