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The new features in unittest for Python 2.7 backported to Python 2.4+.

Project description

unittest2 is a backport of the new features added to the unittest testing framework in Python 2.7. It is tested to run on Python 2.4 - 2.6.

To use unittest2 instead of unittest simply replace import unittest with import unittest2.

unittest2 is maintained in a mercurial repository. The issue tracker is on google code:

Classes in unittest2 derive from the appropriate classes in unittest, so it should be possible to use the unittest2 test running infrastructure without having to switch all your tests to using unittest2 immediately. Similarly you can use the new assert methods on unittest2.TestCase with the standard unittest test running infrastructure. Not all of the new features in unittest2 will work with the standard unittest test loaders and runners however.

New features include:

  • addCleanups - better resource management
  • many new assert methods including better defaults for comparing lists, sets, dicts unicode strings etc and the ability to specify new default methods for comparing specific types
  • assertRaises as context manager, with access to the exception afterwards
  • test discovery and new command line options (including failfast and better handling of ctrl-C during test runs)
  • class and module level fixtures: setUpClass, tearDownClass, setUpModule, tearDownModule
  • test skipping and expected failures
  • new delta keyword argument to assertAlmostEquals for more useful comparison and for comparing non-numeric objects (like datetimes)
  • load_tests protocol for loading tests from modules or packages
  • startTestRun and stopTestRun methods on TestResult
  • various other API improvements and fixes


Command line usage

In Python 2.7 you invoke the unittest command line features (including test discover) with python -m unittest <args>. As unittest is a package, and the ability to invoke packages with python -m ... is new in Python 2.7, we can’t do this for unittest2.

Instead unittest2 comes with a script unit2. Command line usage:

unit2 discover
unit2 -v test_module

There is also a copy of this script called, useful for Windows which uses file-extensions rather than shebang lines to determine what program to execute files with. Both of these scripts are installed by distutils.

Until I write proper documentation, the best information on all the new features is the development version of the Python documentation for Python 2.7:

Look for notes about features added or changed in Python 2.7.


unittest2 is already in use for development for development of distutils2.


Differences between unittest2 and unittest in Python 2.7:

assertItemsEqual does not silence Py3k warnings as this uses warnings.catch_warnings() which is new in Python 2.6 (and is used as a context manager which would be a pain to make work with Python 2.4).

The underlying dictionary storing the type equality functions on TestCase is a custom object rather than a real dictionary. This allows TestCase instances to be deep-copyable on Python versions prior to 2.7.

TestCase.longMessage defaults to True because it is better. It defaults to False in Python 2.7 for backwards compatibility reasons.

python -m package doesn’t work in versions of Python before Python 2.7. The command line features of unittest2 are provided by a unit2 (and script instead.


A TestResult object with unexpected successes returns True for result.wasSuccessful(). Difficult to know if this is the correct behaviour or not.

If a dotted path name is used for test discovery then a globally installed module/package will still be used in preference of one in the current directory. When doing discovery from a dotted path name we could check for this specific case.

The removeHandler decorator could also be a context manager.

Issue 8313:, <unprintable AssertionError object> message in unittest tracebacks, is hard to fix in versions of Python before 2.7. The fix in Python 2.7 relies on changes to both the traceback module and traceback objects. As the issue is rare I am leaving it unfixed in unittest2.

There are several places in unittest2 (and unittest) that call str(...) on exceptions to get the exception message. This can fail if the exception was created with non-ascii unicode. This is rare and I won’t address it unless it is actually reported as a problem for someone.


2010/06/06 - 0.4.2

Improved help message for unit2 discover -h.

SkipTest in unittest.TestCase.setUpClass or setUpModule is now reported as a skip rather than an error.

Excessively large diffs due to TestCase.assertSequenceEqual are no longer included in failure reports. (Controlled by TestCase.maxDiff.)

Matching files during test discovery is done in TestLoader._match_path. This method can be overriden in subclasses to, for example, match on the full file path or use regular expressions for matching.

Addition of a setuptools compatible entrypoint for the unit2 test runner script. Contributed by Chris Withers.

Tests fixed to be compatible with Python 2.7, where deprecation warnings are silenced by default.

Feature parity with unittest in Python 2.7 RC 1.

2010/05/09 - 0.4.1

If test discovery imports a module from the wrong location (usually because the module is globally installed and the user is expecting to run tests against a development version in a different location) then discovery halts with an ImportError and the problem is reported.

Added docstrings to assertRegexpMatches and assertNotRegexpMatches.

Putting functions in test suites no longer crashes.

Feature parity with unittest in Python 2.7 Beta 2.

2010/04/08 - 0.4.0

Addition of removeHandler for removing the control-C handler.

delta keyword argument for assertAlmostEqual and assertNotAlmostEqual.

Addition of -b command line option (and TestResult.buffer) for buffering stdout / stderr during test runs.

Addition of TestCase.assertNotRegexpMatches.

Allow test discovery using dotted module names instead of a path.

All imports requiring the signal module are now optional, for compatiblity with IronPython (or other platforms without this module).

Tests fixed to be compatible with nosetest.

2010/03/26 - 0.3.0

assertSameElements removed and assertItemsEqual added; assert that sequences contain the same elements.

Addition of -f/–failfast command line option, stopping test run on first failure or error.

Addition of -c/–catch command line option for better control-C handling during test runs.

Added BaseTestSuite, for use by frameworks that don’t want to support shared class and module fixtures.

Skipped test methods no longer have setUp and tearDown called around them.

Faulty load_tests functions no longer halt test discovery.

Using non-strings for failure messages now works.

Potential for UnicodeDecodeError whilst creating failure messages fixed.

Split out monolithic test module into a package.

BUGFIX: Correct usage message now shown for unit2 scripts.

BUGFIX: __unittest in module globals trims frames from that module in reported stacktraces.

2010/03/06 - 0.2.0

The TextTestRunner is now compatible with old result objects and standard (non-TextTestResult) TestResult objects.

setUpClass / tearDownClass / setUpModule / tearDownModule added.

2010/02/22 - 0.1.6

Fix for compatibility with old TestResult objects. New tests can now be run with nosetests (with a DeprecationWarning for TestResult objects without methods to support skipping etc).


Initial release.


For before the Python 2.7 final release:

  • Issue 8564 on the Python bug tracker
  • Document SkipTest, BaseTestSuite and _ErrorHolder

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