Earnest Engineer

This I wrote to answer a question that came up when we were discussing our software process and I was training developers on how to unit test. It seems a simple enough question, but I kept pondering it and delving deeper until I realized I needed to write this monograph. What unit tests should we write? How do we know what to test? Ideally, unit tests should cover every path through the code. It should be your chance to see every path through your code works as expected and as needed. If you are practicing Test Driven Development then it's implied everything gets a test. In the real world, you might not be allowed to test everything - for instance, if the testing suite ends up taking a week to run, then the world will have changed by the time it finishes and the test results will be obsolete. Unit testing at it's basic is testing an object, a method - the smallest unit of your code that it can test independently. It should test the inputs "goes into" an