Add unittest.TestCase.assertMappingEqual

Feature or enhancement

Proposal:

unittest.TestCase has assertDictEqual which requires both arguments to be dict's. Would it make sense to add assertMappingEqual which would weaken this requirement to Mapping?

For example, this would be helpful with immutabledict which is not a dict.

Possible implementation (pseudocode) is to change the existing code:

def assertDictEqual(self, d1, d2, msg=None):
  # [existing] assert d1 and d2 are dict's
  # [existing] check that items are the same  

to

def assertMappingEqual(self, d1, d2, msg=None):
  # [new] assert d1 and d2 are Mapping's
  # [existing] check that items are the same  

def assertDictEqual(self, d1, d2, msg=None):
  # [existing] assert d1 and d2 are dict's
  self.assertMappingEqual(d2, d2, msg)

Considerations and comparison:

1. Alternatively, the checks in assertDictEqual could be weakened to Mapping, however this might introduce problems into existing tests.

2. For sequences, there are assertListEqual and assertSequenceEqual. Here assertListEqual simply calls assertSequenceEqual without any type checks.

3. For sets, there are assertSetEqual and assertCountEqual. Here the implementations are different. assertSetEqual does not check the types of the arguments, but requires them to have the method difference. assertCountEqual only requires the arguments to be iterables.

4. It is possible to replace assertMappingEqual(a, b) with assertDictEqual({**a}, {**b}), however this is arguably ugly.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-121113

Start from the unittest.TestCase.assertDictEqual entry point and review the linked PR gh-121113. Determine whether a separate assertMappingEqual API is appropriate and preserve the existing dictionary behavior; done means the proposed mapping comparison is implemented with coverage for Mapping inputs and existing behavior remains intact.