Convert tests to use subtests with t.Run

[kisielk]

Just a maintenance task, but it will make test reporting cleaner in case of failure:

https://blog.golang.org/subtests

[kanozec]

I think I can take this, but I'm not familiar with the go test. I just have some practice before.
Could you give me some advice for which test file to refactor first.
I think that would be really helpful, thx.

[stale]

This issue has been automatically marked as stale because it hasn't seen a recent update. It'll be automatically closed in a few days.

[kisielk]

Still valid

[fharding1]

I'm happy to take this on for the remainder of the tests. Also, should I update old_test.go, or is that pretty much unmaintained (per comment // Old tests ported to Go1. This is a mess. Want to drop it one day.).

[fharding1]

Should this issue be closed? Seems like most every test that it makes sense for is using subtests now.