update tests to zio-test

[TimPigden]

I'm volunteering to do this. I'll build a couple of doc pages around them at the same time - could be useful. @iravid any reason not to do this?

[iravid]

Thanks @TimPigden! Would be great to have the tests ported to zio-test.

[TimPigden]

while I could close this - I'll leave it open as changes to zio-test in RC17 mean that these could be further streamlined - plus @adamgfraser 's suggestion for mods in #61
I'll take this when I get back to documenting the tests in md

[TimPigden]

actually that's RC18

[iravid]

Thank you @TimPigden for porting the tests!