All the normal rules of programming apply to tests: stay organized, reduce duplication, and don't take on more technical debt than you need. For small projects, it's easy to create and manage single test files. Large or important projects need more thought and care. Where do you put your tests? How do you organize them between files? What options do you have to reduce complexity to manageable levels?
This chapter's labs explain how to organize your test files into test suites, know and improve the reach of your tests, write your own custom testing libraries, and interpret test results.