Mark Seemann • 12/22/2025

Test-specific Eq

The article discusses a common challenge in unit testing: asserting equality for complex data types that are not instances of the Eq typeclass. Using a Haskell-based example of a cellular automaton modeling finches, it proposes creating test-specific Eq instances to enable cleaner, more direct assertions (like `actual @?= expected`) instead of writing verbose, tautological checks. It examines the trade-offs and practicality of this approach within a constrained codebase.

0 comments

#functional programming #unit testing #test automation