It seems that some code in UserList, UserDict and UserString is not covered by tests. Some of existing tests are too lenient -- they tests the value of the result, but not its type. Some tests do not test particular combination of argument types. For some methods tests are absent at all. And some code is a pure optimization -- when remove it, the generic slower implementation is used. It is not always possible to test this.

The following PR adds more tests for UserList, UserDict and UserString. Some tests are added to generic tests, so new tests are also added for str, bytes, bytearray, list, tuple, deque, etc.

Linked PRs

• gh-145144: Add more tests for UserList, UserDict, etc #145145
• [3.14] gh-145144: Add more tests for UserList, UserDict, etc (GH-145145) #146290
• [3.13] gh-145144: Add more tests for UserList, UserDict, etc (GH-145145) #146296