The project helps to create automatically a Comparator typeclass to be used in a regression test
The Comparator type class can say whether two values are equals and a detail of what are the differences between these two values.
The project constructs instances for a large common use cases like List, Map, Double, String, Int. It can compose in many ways to match the required type
The comparator of Double is special because It should accept some errors due to numerical errors. In order to construct a doube comparator, we should define an implicit special object called AcceptanceError:
case class AcceptanceError(relative: Double, absolute: Double)The 2 values x and y are accepted when (x - y) / x < relative. If x == 0 or y == 0 then the absolute value is used: abs(x - y) < absolute
In tests, we should compare 2 objets by:
Comparator.assertEqual(first, second)It will raise exception if first != second in print to the console the exact differences
The project is quite simpe and it's an excellent way to learn shapeless, just copy/paste 3 files into your project and explore it