If you write a Python package, various tests might be spread out through the package. The module discover finds, imports, and runs these test cases. The basic call from the command line is:
python -m unittest discover
It starts looking for test cases in the current directory and recurses the directory tree downward to find Python objects with the 'test' string contained in its name. The command takes optional arguments. Most important are -s to modify the start directory and -p to define the pattern to recognize the tests:
python -m unittest discover -s '.' -p 'Test*.py'
