On Tue, Mar 01, 2022 at 12:56:02PM -0500, Daneel Yaitskov wrote:
I noticed, that I pay more attention than I should, when working with assertions, because I am not sure about argument order i.e. whether the expected value goes first or vice-versa. Does anybody have similar thought?
The documentation is quite clear: https://hackage.haskell.org/package/HUnit-1.6.2.0/docs/Test-HUnit-Base.html#...
Such subtle detail should be easy to grasp with regular practice, but I observe difficulties and I suspect that there is a logical reason for that.
I spell "assertEqual" expression as: "Assert that x equals to y" "y" sounds like a model value (i.e. expected value).
As a combinator that can be curried, -- Check variable given against fixed wanted assertEqual prefix wanted :: (Eq a, Show a) => a -> Assertion is I think more useful than: -- Check variable wanted against fixed given. assertEqual prefix given :: (Eq a, Show a) => a -> Assertion
Similar issue with test fixing - I always have to check first, that an expected value is actually one. There is no type safety preventing mixing arguments.
The test works either way of course, the only thing that changes is the error message on failure. You could implement a type-safe wrapper: newtype Given a = Given a newtype Wanted a = Wanted a checkEq :: (Eq a, Show a) => String -> Given a -> Wanted a -> Assertion checkEq prefix (Given x) (Wanted y) = assertEqual prefix y x Then always call via: checkEq "Oops" (Given (2 + 2)) (Wanted 5) -- Viktor.