When spying on a staticmethod or classmethod defined directly on a

class (passing the method plus owner=), unspy() replaced the

descriptor on the class with a plain function, instead of restoring the

original staticmethod or classmethod.
The cause was in how the spy records the value to restore. When the

owner does not need patching (a class that owns the attribute directly,

not slippery, not inherited), the spy stored self.orig_func as the

restore value. For a staticmethod or classmethod, orig_func is the

function obtained through attribute access, which has already been

unwrapped by the descriptor. On unspy(), that unwrapped function was

assigned back onto the class, discarding the descriptor.
While spied, everything still worked, because the spy swaps the code

object in place and the descriptor keeps pointing at the same function.

The corruption only appeared after unspy(): the attribute was now a

plain function, so a later call through an instance bound the instance

as the first positional argument. For a staticmethod this raised a

TypeError. For a classmethod the instance was silently passed where

the class was expected.
We now store the attribute value exactly as defined in the owner

class dict for this case, matching what the owner-patching path

already does, so the descriptor is preserved across unspy().
This also removes a workaround in the test base class that manually

restored MathClass.class_do_math after each test. That workaround

existed only to paper over this bug, and it corrupted the classmethod

descriptor for later tests. One test

(test_construction_with_call_fake_and_classmethod) depended on that

corruption, asserting object identity across two classmethod accesses;

it now compares by equality, which is correct for a classmethod that

returns a fresh bound method each time.

Commented out the fix and saw the new unit tests fail.
Ran the full test suite on Python 3.14.
Verified all staticmethod and classmethod tests pass in isolation,

  confirming they no longer depend on inter-test state.