Remove the state parameter from fixture functions that do not return state

[lexi-lambda]

Given that state is so infrequently used as it is, and given that it’s very easy to ignore unused return values, I think the state argument should be removed from unTestFixture and logTestFixture, so their type signatures should be as follows:

unTestFixture :: TestFixture r () () a -> r (WS () ()) -> a
logTestFixture :: TestFixture r w () a -> r (WS w ()) -> w

With some nice type aliases (maybe making TestFixture an opaque newtype instead of a type alias) I think this would make the API a lot less confusing than it currently is.

[jxv]

+1 for newtypes

+1 for removing unit ()