unittest is based on Erich Gamma's JUnit and Kent Beck's Smalltalk testing framework.
It contains the core framework classes that form the basis of the test cases and suites (TestCase, TestSuite and so on), and also a text-based utility class for running the tests and reporting the results (TextTestRunner).
The test cases of the module "unittest" are not defined inside of the module, which has to be tested, like in doctest.
Program documentation and test descriptions are separate from each other.