You write tests - but are they valuable tests? Carl and Richard talk to Egil Hansen about his approach to creating tests for applications. Egil discusses the types of testing and who they impact. Testing isn't only for you! Valuable tests are also durable, being able to persist between changes where it makes sense, and help to understand when updates are going to create problems. The role of LLMs in generating code comes into play: should AI write your tests, evaluate them, or do both? Lots of great thinking from someone who's been helping developers build better tests for years!