Expert Python Programming - Third Edition

Testing coverage

Code coverage is a very useful metric that provides objective information on how well project code is tested. It is simply a measurement of how many and which lines of code are executed during the test execution. It is often expressed as a percentage, and 100% coverage means that every line of code was executed during tests.

The most popular code coverage tool is called the coverage, and is freely available on PyPI. Its usage is very simple and consists only of two steps. The first step is to execute the coverage run command in your shell with the path to your script/program that runs all the tests, as follows:

$ coverage run --source . `which py.test` -v ===================== test session starts ====================== platformdarwin ...