Flaky is a plugin for nose or pytest that automatically reruns flaky tests.
Ideally, tests reliably pass or fail, but sometimes test fixtures must rely on components that aren't 100% reliable. With flaky, instead of removing those tests or marking them to @skip, they can be automatically retried.
For more information about flaky, see
this presentation <http://opensource.box.com/flaky/>_.
Marking tests flaky
To mark a test as flaky, simply import flaky and decorate the test with @flaky: .. code-block:: python from flaky import flaky .. code-block:: python @flaky def test_something_that_usually_passes(self): value_to_double = 21 result = get_result_from_flaky_doubler(value_to_double) self.assertEqual(result, value_to_double * 2, 'Result doubled incorrectly.') By default, flaky will retry a failing test once, but that behavior can be overridden by passing values to the flaky decorator. It accepts two parameters: max_runs, and min_passes; flaky will run tests up to max_runs times, until it has succeeded min_passes times. Once a test passes min_passes times, it's considered a success; once it has been run max_runs times without passing min_passes times, it's considered a failure. .. code-block:: python @flaky(max_runs=3, min_passes=2) def test_something_that_usually_passes(self): """This test must pass twice, and it can be run up to three times.""" value_to_double = 21 result = get_result_from_flaky_doubler(value_to_double) self.assertEqual(result, value_to_double * 2, 'Result doubled incorrectly.') Marking a class flaky +++++++++++++++++++++ In addition to marking a single test flaky, entire test cases can be marked flaky: .. code-block:: python @flaky class TestMultipliers(TestCase): def test_flaky_doubler(self): value_to_double = 21 result = get_result_from_flaky_doubler(value_to_double) self.assertEqual(result, value_to_double * 2, 'Result doubled incorrectly.') @flaky(max_runs=3) def test_flaky_tripler(self): value_to_triple = 14 result = get_result_from_flaky_tripler(value_to_triple) self.assertEqual(result, value_to_triple * 3, 'Result tripled incorrectly.') The @flaky class decorator will mark test_flaky_doubler as flaky, but it won't override the 3 max_runs for test_flaky_tripler (from the decorator on that test method). Pytest marker +++++++++++++ When using ``pytest``, ``@pytest.mark.flaky`` can be used in place of ``@flaky``. Don't rerun certain types of failures
Depending on your tests, some failures are obviously not due to flakiness. Instead of rerunning after those failures, you can specify a filter function that can tell flaky to fail the test right away.
.. code-block:: python
def is_not_crash(err, *args): return not issubclass(err, ProductCrashedError) def test_something(): raise ProductCrashedError def test_something_else(): raise ProductCrashedError
Flaky will run
test_something twice, but will only run
It can also be used to incur a delay between test retries:
.. code-block:: python
import time def delay_rerun(*args): time.sleep(1) return True def test_something_else(): ...
Activating the plugin
Like any nose plugin, flaky can be activated via the command line: .. code-block:: console nosetests --with-flaky With pytest, flaky will automatically run. It can, however be disabled via the command line: .. code-block:: console pytest -p no:flaky Command line arguments
No Flaky Report +++++++++++++++
--no-flaky-report to suppress the report at the end of the run detailing flaky test results.
Shorter Flaky Report ++++++++++++++++++++
--no-success-flaky-report to suppress information about successful flaky tests.
Force Flaky +++++++++++
--force-flaky to treat all tests as flaky.
--min-passes=MIN_PASSES to control the behavior of flaky if
is specified. Flaky decorators on individual tests will override these defaults.
Additional usage examples are in the code - see test/test_nose/test_nose_example.py and test/test_pytest/test_pytest_example.py
To install, simply:
.. code-block:: console
pip install flaky
Flaky is tested with the following test runners and options:
Nosetests. Doctests cannot be marked flaky.
Py.test. Works with
pytest-xdist but not with the
--boxed option. Doctests cannot be marked flaky.
Create a virtual environment and install packages - .. code-block:: console mkvirtualenv flaky pip install -r requirements-dev.txt Testing
Run all tests using -
.. code-block:: console
The tox tests include code style checks via pycodestyle and pylint.
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