OpenStack Networking (Neutron)
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Neutron Style Commandments

Neutron Specific Commandments

Some rules are enforced by neutron-lib hacking factory while other rules are specific to Neutron repository.

Below you can find a list of checks specific to this repository.

  • [N322] Detect common errors with assert_called_once_with
  • [N328] Detect wrong usage with assertEqual
  • [N330] Use assertEqual(empty, observed) instead of

    assertEqual(observed, empty)

  • [N331] Detect wrong usage with assertTrue(isinstance()).
  • [N332] Use assertEqual(expected_http_code, observed_http_code) instead of

    assertEqual(observed_http_code, expected_http_code).

  • [N334] Use unittest2 uniformly across Neutron.
  • [N340] Check usage of <module>.i18n (and neutron.i18n)
  • [N341] Check usage of _ from python builtins
  • [N343] Production code must not import from neutron.tests.*
  • [N344] Python 3: Do not use filter(lambda obj: test(obj), data). Replace it with [obj for obj in data if test(obj)].


When adding a new hacking check to this repository or neutron-lib, make sure its number (Nxxx) doesn't clash with any other check.


As you may have noticed, the numbering for Neutron checks has gaps. This is because some checks were removed or moved to neutron-lib.

Creating Unit Tests

For every new feature, unit tests should be created that both test and (implicitly) document the usage of said feature. If submitting a patch for a bug that had no unit test, a new passing unit test should be added. If a submitted bug fix does have a unit test, be sure to add a new one that fails without the patch and passes with the patch.

All unittest classes must ultimately inherit from testtools.TestCase. In the Neutron test suite, this should be done by inheriting from neutron.tests.base.BaseTestCase. If the third party unittest library has to be used directly then it is recommended to use unittest2 as it contains bug fixes to unittest for all versions of Python prior to version 3.5.

All setUp and tearDown methods must upcall using the super() method. tearDown methods should be avoided and addCleanup calls should be preferred. Never manually create tempfiles. Always use the tempfile fixtures from the fixture library to ensure that they are cleaned up.