This worked in Python 3.6, but in Python 3.7 and later creating a mock with a spec specifying a subscripted generic class does not mock any of the attributes of the class, because those attributes are not returned by dir().

For example:

# cat test.py
from typing import Generic, TypeVar
from unittest import mock

T = TypeVar('T')

class Foo(Generic[T]):
    def bar(self) -> None:
        pass

m = mock.MagicMock(spec=Foo[int])
m.bar()


# python3.11 test.py
Traceback (most recent call last):
  File "/root/test.py", line 11, in <module>
    m.bar()
    ^^^^^^^
  File "/usr/lib/python3.11/unittest/mock.py", line 635, in __getattr__
    raise AttributeError("Mock object has no attribute %r" % name)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: Mock object has no attribute 'bar'