Writing and running automated tests can go a long way to help maintain the quality and reliability of a code base. Tests help ensure the code you've written executes the way you expect it to. However, even though automated tests are a great tool for helping to ensure quality over the years in which people will contribute to the code, they are not sufficient in and of themselves. It may be inevitable that all software products will reach a point of obsolescence no matter how much work is done to keep them current. The inherent problem is that if we view tests as constraints upon what the software system under test can be, then as we add more and more tests over the years, we will have more and more constraints on the shape our software is allowed to take. It then seems we must reach an inevitable point where we can no longer change our software system without violating a constraint, i.e. causing a test to fail. In more practical terms, we'll more likely first reach a situat...