Testing Without Mocks: A Pattern Language (2023)

Automated tests are important. Without them, programmers waste a huge amount of time manually checking and fixing their code. Unfortunately, many automated tests also waste a huge amount of time. The easy, obvious way to write tests is to make broad tests that are automated versions of manual tests. But they’re flaky and slow. Folks in the know use mocks and spies (I say “mocks” for short in this article) to write isolated interaction-based tests. Their tests are reliable and fast, but they tend to “lock in” implementation, making refactoring difficult, and they have to be supplemented with broad tests. It’s also easy to make poor-quality tests that are hard to read, or end up only testing themselves. Bad tests are a sign of bad design, so some people use techniques such as Hexagonal Architecture and functional core, imperative shell to separate logic from infrastructure. (Infrastructure is code that involves external systems or state.) It fixes the problem... for logic. But infrast ... Read full article.