Why unit test? (cont'd)

• Test cases provide a sample use of your code. That is, programmers who want to use your code can read your unit tests to see how you expect client code to use it.

  Speaker's notes:

  If you are distributing Free Software or Open Source code, you can ship your unit tests to show others how to use your classes and modules. Even with code written for "internal use," unit tests provide simple examples of how you expect clients to interact with a unit. That way, you may be able to avoid writing separate sample programs for other programmers who need to use your code. They can just read the unit tests.

• In a very dynamic language like Python, unit tests provide added safety. Unit tests make up for some of the compile time checks that you lose.

  Speaker's notes:

  For those who have never programmed in a less dynamic language, such as C++ or Java, you may not realize how important some developers feel compile-time checks are. In these languages, code is written to push as much error detection as possible to compile time so that errors won't be discovered by QA or customers at run time. In the absence of compile time checks, thorough unit testing is even more important because it can catch many simple bugs (NameErrors and such) that may only be detectable at runtime in Python.