Extending and customizing nose with plugins

nose has plugin hooks for loading, running, watching and reporting on tests and test runs. If you don’t like the default collection scheme, or it doesn’t suit the layout of your project, or you need reports in a format different from the unittest standard, or you need to collect some additional information about tests (like code coverage or profiling data), you can write a plugin to do so. See the section on writing plugins for more.

nose also comes with a number of built-in plugins, such as:

  • Output capture

    Unless called with the -s (--nocapture) switch, nose will capture stdout during each test run, and print the captured output only for tests that fail or have errors. The captured output is printed immediately following the error or failure output for the test. (Note that output in teardown methods is captured, but can’t be output with failing tests, because teardown has not yet run at the time of the failure.)

  • Assert introspection

    When run with the -d (--detailed-errors) switch, nose will try to output additional information about the assert expression that failed with each failing test. Currently, this means that names in the assert expression will be expanded into any values found for them in the locals or globals in the frame in which the expression executed.

    In other words, if you have a test like:

    def test_integers():
        a = 2
        assert a == 4, "assert 2 is 4"

    You will get output like:

    File "/path/to/file.py", line XX, in test_integers:
         assert a == 4, "assert 2 is 4"
    AssertionError: assert 2 is 4
      >>  assert 2 == 4, "assert 2 is 4"

    Please note that dotted names are not expanded, and callables are not called in the expansion.

See below for the rest of the built-in plugins.

Using Builtin plugins

See Batteries included: builtin nose plugins