A common question, especially within organizations that rely heavily on manual testing, is Why should we use unit instead of functional and integration testing? This question in itself is flawed. Unit testing does not replace other types of testing. Instead, unit testing reduces the scope of other types of tests. By its nature, unit testing is easier and faster to write than any other type of tests, thus reducing the cost and time to market (TTM). Due to the reduced time to write and run them, they tend to detect problems much sooner. The faster we detect problems, the cheaper it is to fix them. A bug that was detected minutes after it was created is much easier to fix than if that same bug was found days, weeks, or even months after it was made.