Question

Does HUnit have some way of doing approximate equalities? Clearly, this fails:

test1 = TestCase (assertEqual "Should equal" (get_scores) [(0.3, 0.3), (0.6, 0.36), (1.0, 0.3399999)])

Answer 1

Note: I don’t know if there’s a correct/official/accepted way to do this.

---

Here’s the source code for assertEqual:

assertEqual :: (Eq a, Show a) => String -- ^ The message prefix 
                              -> a      -- ^ The expected value 
                              -> a      -- ^ The actual value
                              -> Assertion
assertEqual preface expected actual =
  unless (actual == expected) (assertFailure msg)
 where msg = (if null preface then "" else preface ++ "\n") ++
             "expected: " ++ show expected ++ "\n but got: " ++ show actual

Based on that and on JUnit’s function for testing double equality, we could create our own in the same style:

import Control.Monad (unless)

assertEquals ::   String  -- ^ The message prefix
               -> Double  -- ^ The maximum difference between expected and actual
               -> Double  -- ^ The expected value
               -> Double  -- ^ The actual value
               -> Assertion
assertEquals preface delta expected actual = 
  unless (abs (expected - actual) < delta) (assertFailure msg)
 where msg = ... same as above ...