The test package contains all regression tests for Python as well as the modules test.test_support and test.regrtest. test.test_support is used to enhance your tests while test.regrtest drives the testing suite.
Each module in the test package whose name starts with "test_" is a testing suite for a specific module or feature. All new tests should be written using the unittest module; using unittest is not required but makes the tests more flexible and maintenance of the tests easier. Some older tests are written to use doctest and a ``traditional'' testing style; these styles of tests will not be covered.