Error messages should print arrays

[honno]

I found for sort tests that out[<idx>]=foo is useful, but it'd be nicer to also see the input and out arrays after a newline. I should review the pytest helpers so we display this information for all tests.

[honno]

#89 fixed this for the elwise/op tests. Definitely a case-by-case kind of thing, so will close and just keep this back-of-mind.