I hope it is no secret that testing of written code is as important as writing the code itself, and sometimes even more important. Writing unit test for C#/Java/…code coverage is the responsibility of each software developer.
However, there is not always an opportunity to use autotests. For example, until recently, there were no good computer-aided testing systems for SQL Server, and many people had to create self-made products that were expensive to support and develop. To tell the truth, I was doing that too.