In my experience, tests are very important because without them it's much harder to make sure the existing logic is the same after a change or a refactor. It's

In my experience, tests are very important because without them it's much harder to make sure the existing logic is the same after a change or a refactor. It's a great idea to keep in the back of one's mind how they are going to test what they are working on. TDD is a very structured way of doing that so it could be beneficial but not an absolute necessity.