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discover 0.4.0

Test discovery for unittest. Backported from Python 2.7 for Python 2.4+

This is the test discovery mechanism and load_tests protocol for unittest backported from Python 2.7 to work with Python 2.4 or more recent (including Python 3).


Test discovery is just part of what is new in unittest in Python 2.7. All of the new features have been backported to run on Python 2.4-2.6, including test discovery. This is the unittest2 package.

discover can be installed with pip or easy_install. After installing switch the current directory to the top level directory of your project and run:

python -m discover

(If you have setuptools or distribute installed you will also have a discover script available.)

This will discover all tests (with certain restrictions) from the current directory. The discover module has several options to control its behavior (full usage options are displayed with python -m discover -h):

Usage: [options]

  -v, --verbose    Verbose output
  -s directory     Directory to start discovery ('.' default)
  -p pattern       Pattern to match test files ('test*.py' default)
  -t directory     Top level directory of project (default to
                   start directory)

For test discovery all test modules must be importable from the top
level directory of the project.

For example to use a different pattern for matching test modules run:

python -m discover -p '*'

(For UNIX-like shells like Bash you need to put quotes around the test pattern or the shell will attempt to expand the pattern instead of passing it through to discover. On Windows you must not put quotes around the pattern as the Windows shell will pass the quotes to discover as well.)

Test discovery is implemented in As well as using discover as a command line script you can import DiscoveringTestLoader, which is a subclass of unittest.TestLoader, and use it in your test framework.

This method finds and returns all test modules from the specified start directory, recursing into subdirectories to find them. Only test files that match pattern will be loaded. (Using shell style pattern matching.)

All test modules must be importable from the top level of the project. If the start directory is not the top level directory then the top level directory must be specified separately.

The load_tests protocol allows test modules and packages to customize how they are loaded. This is implemented in discover.DiscoveringTestLoader.loadTestsFromModule. If a test module defines a load_tests function then tests are loaded from the module by calling load_tests with three arguments: loader, standard_tests, None.

If a test package name (directory with matches the pattern then the package will be checked for a load_tests function. If this exists then it will be called with loader, tests, pattern.


The default pattern for matching tests is test*.py. The ‘.py’ means that it will match test files and not match package names. You can change this by changing the pattern using a command line option like -p 'test*'.

If load_tests exists then discovery does not recurse into the package, load_tests is responsible for loading all tests in the package.

The pattern is deliberately not stored as a loader attribute so that packages can continue discovery themselves. top_level_dir is stored so load_tests does not need to pass this argument in to is maintained in a google code project (where bugs and feature requests should be posted):

The latest development version of can be found at:


2010/06/11 0.4.0

  • Addition of a setuptools compatible test collector. Set “test_suite = ‘discover.collector’” in “ test” will start test discovery with default parameters from the same directory as the
  • Allow test discovery using dotted module names instead of a path.
  • Addition of a setuptools compatible entrypoint for the discover script.
  • A faulty load_tests function will not halt test discovery. A failing test is created to report the error.
  • 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.
  • Matching files during test discovery is done in DiscoveringTestLoader._match_path. This method can be overriden in subclasses to, for example, match on the full file path or use regular expressions for matching.
  • Tests for discovery ported from unittest2. (The tests require unittest2 to run.)

Feature parity with the TestLoader in Python 2.7 RC 1.

2010/02/07 0.3.2

  • If load_tests exists it is passed the standard tests as a TestSuite rather than a list of tests.

2009/09/13 0.3.1

  • Fixed a problem when a package directory matches the discovery pattern.

2009/08/20 0.3.0

  • Failing to import a file (e.g. due to a syntax error) no longer halts discovery but is reported as a failure.
  • Discovery will not attempt to import test files whose names are not valid Python identifiers, even if they match the pattern.
File Type Py Version Uploaded on Size
discover-0.4.0.tar.gz (md5) Source 2010-06-11 8KB
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