At the very minimum you should write a test each time you find a bug, so that it doesn't happen again. If you already know what the problem is writing a test ca

At the very minimum you should write a test each time you find a bug, so that it doesn't happen again. If you already know what the problem is writing a test case for it should be simple. The only time writing a test suite would be hard, is if you are doing something special like writing a VM guest or embedded, where automating tests take much more work. Even then, just knowing that the basics work all the time is very beneficial, even if the test suite is small.