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gocept.testing 1.9

A collection of test helpers, additional assertions, and the like.

Latest Version: 1.10.1

This package collects various helpers for writing tests.


An assertion which is very helpful when using Testbrowser with unittest.TestCase (instead of doctests).

Some examples:

class MyTest(unittest.TestCase, gocept.testing.assertion.Ellipsis):
# [...]

self.assertEllipsis('', 'foo bar qux')
# -> nothing happens

self.assertEllipsis('foo', 'bar')
# -> AssertionError: Differences (ndiff with -expected +actual):
     - foo
     + bar

self.assertNotEllipsis('foo', 'foo')
# -> AssertionError: "Value unexpectedly matches expression 'foo'."

To use, inherit from gocept.testing.assertion.Ellipsis in addition to unittest.TestCase.

assertStartsWith, assertEndsWith

class MyTest(unittest.TestCase, gocept.testing.assertion.String):

    def test_something(self):
        self.assertStartsWith('foo', 'foobar') # --> pass
        self.assertEndsWith('bar', 'foobar') # --> pass
        self.assertStartsWith('qux', 'foobar') # --> fail
        self.assertEndsWith('qux', 'foobar') # --> fail


The opposite of assertRaises(), this is an assertion that makes some tests more readable. As assertRaises(), it can be used as as context manager, too:

class MyTest(unittest.TestCase, gocept.testing.assertion.Exceptions):
# [...]

self.assertNothingRaised(do_something, 1, 2, 3)

with self.assertNothingRaised():
    do_something(1, 2, 3)

mock patch context

gocept.testing.mock.Patches collects mock patches that are valid for the whole TestCase, and resets them all in one go in tearDown (this is pending incluion upstream as mock.patcher(), see issue 30):

class MyTest(unittest.TestCase):

    def setUp(self):
        self.patches = gocept.testing.mock.Patches()

    def tearDown(self):

    def test_something(self):
        compile = self.patches.add('re.compile')

It offers three methods:

add:wraps mock.patch()
add_object:wraps mock.patch.object
add_dict:wraps mock.patch.dict

Note that gocept.testing does not declare a dependency on mock to be as lightweight as possible, so clients need to do that themselves.

If you want to save typing, you can mix gocept.testing.mock.PatchHelper into your TestCase, it defines a setUp method that instatiates Patches and a tearDown that calls reset() on it.


This is syntactic sugar around mock.assert_called_with, so you can write:

class MyTest(unittest.TestCase, gocept.testing.mock.Assertions):

    def test_something(self):
        dummy = mock.Mock()
        self.assertCalledWith(dummy, True)

instead of:


Mocking properties

gocept.testing.mock.Property is syntactic sugar directly lifted from the mock documentation that allows you to patch properties like this:

class Dummy(object):

    def foo(self):
        return False

with mock.patch('', gocept.testing.mock.Property()) as foo:
    foo.return_value = 'something else'

Attribute patch context

This has nothing to do with mocks, it’s a convenience helper for setting and automatically resetting attributes of objects:

class MyTest(unittest.TestCase):

    def setUp(self):
        self.patches = gocept.testing.patch.Patches()
        self.subject = MyClass()

    def tearDown(self):

    def test_something(self):
        self.patches.set(self.subject, 'foo', 'two')

Method call patch context

This allows to call a method and reset it later on automatically. At the moment, only methods that take a single parameter are supported, by passing in both the old value (to which it should be reset) and the new value:

class MyTest(unittest.TestCase):

    def setUp(self):
        self.patches = gocept.testing.patch.Patches()

    def tearDown(self):

    def test_something(self):
            zope.component.hooks, 'setSite',
            zope.component.hooks.getSite(), new_site)

Dict patching context manager

gocept.testing.patch.Dict is a context manager allowing to change values in a dict. It restores the original dict at exit. E. g. it can be used to temporarily change values in os.environ:

>>> with gocept.testing.patch.Dict(os.environ, foo='bar', qwe='asdf'):
        print os.environ.get('foo')
>>> print os.environ.get('foo')

Temporary directory

gocept.testing.fixture.TempDir encapsulates the common pattern to create a temporary directory and delete it after the test has run. The name of the directory is avaliable as self.tmpdir. Note that since unittest.TestCase does not call super, you need to mix in TempDir first:

class MyTest(gocept.testing.fixture.TempDir, unittest.TestCase):

    def test_something(self):

Comparing mtimes

gocept.testing.mtime.Newer checks that generated files are at least as new as their source counterparts (similar like make works):

class MyTest(gocept.testing.mtime.Newer, unittest.TestCase):

    source_ext = '.js'
    target_ext = '.min.js'
    message = 'run jsmin to correct this'

    def test_minified_js_files_are_younger_than_non_minified_ones(self):
            'my.package', 'resources/js'))

Retrying flaky tests

gocept.testing.retry is a decorator that calls a function several times (default: 3) if the function raises an exception, it is swallowed, except on the last repetition. This is useful for running flaky tests several times, but only fail when they actually fail each time, not only some of the time:

class MyTest(unittest.TestCase):

    def test_fails_sometimes():
        # ...

Note that this does not play well with py.test, since retry changes the function’s signature to (*args, **kw), so the funcargs-based fixtures of py.test won’t work (and unfortunately, using decorator to alleviate that is not an option due to too much funcargs magic in py.test).


The source code is available in the mercurial repository at

Please report any bugs you find at


1.9 (2013-12-20)

  • Add retry decorator that runs flaky tests several times and only fails when they fail each time.
  • Use py.test instead of zope.testrunner for this package’s own tests.

1.8 (2013-07-17)

  • Python 3 compatibility.
  • Depend on setuptools rather than distribute now that the projects have merged.
  • Use current buildout and recipes for development.

1.7 (2013-04-18)

  • Fix Python-2.6 compatibility of our own test suite.
  • Introduce PatchHelper.

1.6.0 (2013-01-07)

  • Add newer mtime check.

1.5.2 (2012-09-14)

  • .patch.Dict did not restore the keys if an exception occured while the with call.

1.5.1 (2012-09-12)

  • Fixed documentation and faulty 1.5 release.

1.5 (2012-07-10)

  • Add .patch.Dict, a dict patching context manager.

1.4 (2012-06-04)

  • Add TempDir fixture.
  • Add assertStartsWith, assertEndsWith.

1.3.2 (2012-05-09)

  • Allow assertEllipsis to work with mixed unicode/bytes argument (assuming the bytes are UTF-8, as they are with zope.testbrowser).

1.3.1 (2012-02-03)

  • Display original traceback in assertNothingRaised.

1.3 (2011-12-16)

  • Add patch helper for attributes and simple callables.

1.2.1 (2011-12-09)

  • Make Python-3 compatible (at least syntactically).

1.2 (2011-12-09)

1.1 (2011-11-10)

  • Add assertNothingRaised.

1.0 (2011-11-02)

  • first release: assertEllipsis
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