Add a testing helper which verifies the equality/hashing behavior supplied by with_cmp

[exarkun]

One wants to unit test this sort of behavior but characteristic has enough information to automatically generate these tests in most cases.

Perhaps something like MyClassEqualityTests = make_equality_tests(MyClass)?

[hynek]

That sounds great, pull request (for all three cases) maybe? :)

[wallrj]

Twisted has testutils.ComparisonTestsMixin.assertNormalEqualityImplementation https://github.com/twisted/twisted/blob/trunk/twisted/test/testutils.py#L125

• Are all those assertions strictly necessary?
• Should we aim to generate a TestCase class which has separate test methods for all those assertions?
• An example of where this is used is twisted.names.test.test_dns.MessageComparisonTests (https://github.com/twisted/twisted/blob/trunk/twisted/names/test/test_dns.py#L870). But it's painful to have to write a separate test method for comparison of each attribute. So I guess we need to aim to generate test methods for every combination of attribute and equality assertion.

With all that in mind, has anyone got any hints on the best way to implement this?

[hynek]

Removing milestone. Feel free to submit a pull request once you’ve settled on an approach.