The ``py.test`` testing tool makes it easy to write small tests, yet
scales to support complex functional testing.  It provides
- auto-discovery of test modules and functions,
- detailed info on failing `assert statements
  (no need to remember ``self.assert*`` names)
- modular fixtures for managing small or parametrized long-lived
  test resources.
- multi-paradigm support: you can use ``py.test`` to run test suites based
  on unittest (or trial), nose
- single-source compatibility to Python2.4 all the way up to Python3.3,
  PyPy-1.9 and Jython-2.5.1.