The benefits of religiously following a strict Test Driven Development (TDD) approach (always write tests first before code) is a hotly debated topic. No experienced developer should ignore the fact that testing is essential, but there are debatable pros and cons for whether writing unit tests before, during or after has the most benefit.
If your team has a commitment to unit testing there is valuable side benefit to your code quality that can arise by itself but is usually encouraged by more experienced development teams. Overly complex code that doesn’t have a clear or single responsibility, is tightly coupled with other code and/of is excessively long, is hard to test. Complex code is hard to understand and maintain, it’s usually also the source for more defects compared with simpler and easier to understand code. Effective teams always look for areas where they can become more efficient and make their lives easier, and simplifying code to make it easier to test brings these additional benefits with it.
By adopting a mindset that code should be structured so that it is easier to test, you instantly gain from the benefits of simpler code that’s easier to maintain. Win-win all round.