This is how the chapter is organized

The chapter starts with a game scenario, where a bug slips through to production and stays hidden until a user discovers it. This scenario underlines the need for automated testing, and then leads into a discussion on unit testing framework in Python. You will be introduced to the unittest framework and the mock library in Python. The chapter will demonstrate the use of these libraries by writing a few unit tests for our project.

Moving ahead, it shows an example where it is difficult to write a unit test without refactoring the code first (see Refactoring preamble). This is where we take a detour, learn the basics of refactoring, refactor the code, and then develop the last unit test.

Important housekeeping notes

These notes will be useful in case you haven't read the earlier chapters. Otherwise, just move on to the next heading. Like every other chapter, this one has its own set of Python source files. The source code can be downloaded from the...