Tslibs testing6
Kind of all over the place.  There's a lot to be done in terms of making tests.scalars isolate scalar tests, etc.

The added tests in two test_arithmetic files fill out the test matrix started in 17991
> Kind of all over the place.

I haven't be able to look over your changes completely, but given that you say this, is it possible to break up the changes so that they're not so "all over the place" ? Yah, I think its time for a good night's sleep.  I'll start with a coherent chunk of this in the morning.