> Writing quality tests is often much harder than writing quality software I personally believe that tests are how you prove you understand the code you’re wri

> Writing quality tests is often much harder than writing quality software I personally believe that tests are how you prove you understand the code you’re writing, and the changes you’re making. If they’re harder to write than the software, you probably need to further clarify the behavior being tested, but they’re going to be hard sometimes, just as some software is hard. > if I can only write software for which I can also write quality unit tests, I am greatly reducing the space of quality software I can write. I follow TDD, so indeed I only ever write code that I know how to write unit tests for. I haven’t found that TDD restricts the kind of software that I can write, but sometimes it does mean I’m slower to get started in a particular domain. I do find that once over the initial hump my unit tests are a constant companion that make me more comfortable and productive in developing new software. Realistically we both agree that testing software is important, we just disagree in the details. The problems I see with end to end testing are that good patterns for building extensible and loosely coupled end to end testing suites are not as widespread in the industry as they are for unit and even integration tests. My theory as to why is that we assume that end to end tests are going to be slow to run and “heavy” in some sense, and that as such we aren’t running them often enough to force the improvements we need in those suites. I always find it weird when discussions about unit tests become discussions about other kinds of testing, though. I think high (though not necessarily 100%, as that’s arbitrary) and increasing unit test coverage are an empirical sign of code that is being properly maintained. They are not the last word in testing and software QA, they’re closer to being an indicator like using CI and a proper build system instead of a thousand line shell script, and having quality well-maintained documentation. As I said in another comment, I am not going to say that unit tests are the only way to write good software. They’re a powerful tool that I have found helps me and my teams a lot. That’s as far as I will go.