Any sufficiently complex software system has bugs, and those of us who aspire to produce high quality work also seek to not only minimize these, but guarantee that our code does what we say it ought to.

One proven way to eliminate bugs, and ensure that code behaves as documented is to test the program. Easy enough to do by hand, when there isn’t much functionality. However, when the system grows more complex, and there are many possible environmental factors with various permutations, it quickly becomes obvious that we need to automate our testing.