elm-test Basics* elm-test NPM package * elm-explorations/test Elm package * elm-test init command * Running elm-test finds exposed values of type Test

TDD Principles Testing in Elm is easier because it's just expectations of input to output (deterministic) * TDD is a design practice too * Programming by Intention * Writing test first makes code testable & decoupled * Red, green, refactor * YAGNI * "Make the change easy, then make the easy change" * Kent Beck's TDD by Example* * Here's a staring template of a code kata in Elm that you can use to practice * Emily Bache has many more code katas you can practice on her GitHub

Fuzz Testing* Also known as Property-Based Testing * Martin Janiczek's elm-minithesis project * elm-test's view testing API includes Test.Html.Query, Test.Html.Selector, and Test.Html.Event View objects * Testing pyramid * Mocking and stubbing are not needed or possible in Elm * Order dependent test helper in Ruby: i_suck_and_my_tests_are_order_dependent

When to Use Types or Tests* Jeroen's Safe Unsafe Operations blog post * Richard Feldman's talk on Types and Tests * Make Impossible States

Should you test implementation details?* Discourse thread discussing testing internals * Think in terms of a modules responsibility

Higher-Level Testing in Elmelm-program-test Martin Janiczek's elm Europe talk on testing Msg's with ArchitectureTest

• Richard test-update package