Doctest Fixtures

Doctest files, like other tests, can be made more efficient or meaningful or at least easier to write by judicious use of fixtures. nose supports limited fixtures for use with doctest files.

Module-level fixtures

Fixtures for a doctest file may define any or all of the following methods for module-level setup:

  • setup
  • setup_module
  • setupModule
  • setUpModule

Each module-level setup function may optionally take a single argument, the fixtures module itself.

Example:

def setup_module(module):
    module.called[:] = []

Similarly, module-level teardown methods are available, which also optionally take the fixtures module as an argument:

  • teardown
  • teardown_module
  • teardownModule
  • tearDownModule

Example:

def teardown_module(module):
    module.called[:] = []
    module.done = True

Module-level setup executes before any tests are loaded from the doctest file. This is the right place to raise nose.plugins.skip.SkipTest, for example.

Test-level fixtures

In addition to module-level fixtures, test-level fixtures are supported. Keep in mind that in the doctest lexicon, the test is the entire doctest file – not each individual example within the file. So, like the module-level fixtures, test-level fixtures execute once per file. The differences are that:

  • test-level fixtures execute after tests have been loaded, but before any tests have executed.
  • test-level fixtures receive the doctest doctest.DocFileCase loaded from the file as their one required argument.

setup_test(test) is called before the test is run.

Example:

def setup_test(test):
    called.append(test)
    test.globs['count'] = len(called)
setup_test.__test__ = False

teardown_test(test) is alled after the test, unless setup raised an uncaught exception. The argument is the doctest.DocFileCase object, not a unittest.TestCase.

Example:

def teardown_test(test):
    pass
teardown_test.__test__ = False

Bottom line: setup_test, teardown_test have access to the doctest test, while setup, setup_module, etc have access to the fixture module. setup_module runs before tests are loaded, setup_test after.

Note

As in the examples, it’s a good idea to tag your setup_test/teardown_test functions with __test__ = False to avoid them being collected as tests.

Lastly, the fixtures for a doctest file may supply a globs(globs) function. The dict returned by this function will be passed to the doctest runner as the globals available to the test. You can use this, for example, to easily inject a module’s globals into a doctest that has been moved from the module to a separate file.

Example

This doctest has some simple fixtures:

called = []

def globs(globs):
    globs['something'] = 'Something?'
    return globs

def setup_module(module):
    module.called[:] = []

def setup_test(test):
    called.append(test)
    test.globs['count'] = len(called)
setup_test.__test__ = False
    
def teardown_test(test):
    pass
teardown_test.__test__ = False

The globs defined in the fixtures make the variable something available in all examples.

>>> something
'Something?'

The count variable is injected by the test-level fixture.

>>> count
1

Warning

This whole file is one doctest test. setup_test doesn’t do what you think! It exists to give you access to the test case and examples, but it runs once, before all of them, not before each.

>>> count
1

Thus, count stays 1 throughout the test, no matter how many examples it includes.

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