> the moment you put a MOCK in that code is waste. I disagree. I mock the interfaces to other components that have clearly defined output in a clean architectu

> the moment you put a MOCK in that code is waste. I disagree. I mock the interfaces to other components that have clearly defined output in a clean architecture to properly unit test (i.e. a use case). Everything else causes components to be mixed and things to be tested again and again, causing complex and glued together tests. It all depends on proper architecture, which is hard to get right though. We're using kotlin (sealed classes ftw), hexagonal arch + ddd (use cases) and graphql/rest on top. Everything split up by gradle multi modules with architecture tests to verify that modules have not been mixed. We also have a domain module with plain kotlin that implements business logic free of implementation details. With this high separation of concerns unit testing is the only thing you need to do (automated).