[Python] Unexpected failed assert when changing order of python mocks when mocking function...

I am implementing a test for a function func1a() in module1.py using mocks.

The function func1a() calls:

• one function from module2.py: func2a()
• one function from module1.py: func1b()

It appears that the order in which mocks are applied, introduces unexpected effects in my test.

module2.py contains:

def func2a()->None:
return None



module1.py contains:


from module2 import func2a


def func1a()->None:
func2a()
func1b()
return None

def func1b()->None:
return None


The test is implemented this way:


from unittest.mock import MagicMock, Mock, call, patch
import pytest


@patch("module1.func1b")
@patch("module2.func2a")
def test_func1a(
mock_func2a:MagicMock,
mock_func1b:MagicMock,
)->None:
from module1 import func1a
mocks = ( mock_func2a,
mock_func1b,
)
mock_manager = Mock()
for mock in mocks:
mock_manager.attach_mock(mock, "mock_" + mock._extract_mock_name())

expected_calls = [
call.mock_func2a(),
call.mock_func1b(),
]
# When
func1a()

# Then
assert mock_manager.mock_calls == expected_calls


and works perfectly.

However, if I invert the order of the patches and keep the rest of the code identical:

@patch("module2.func2a")
@patch("module1.func1b")
def test_func1a(
mock_func1b:MagicMock,
mock_func2a:MagicMock,
)->None:



I encounter the following assertion error

assert [call.mock_func1b()] == [call.mock_fu...mock_func1b()]

At index 0 diff: call.mock_func1b() != call.mock_func2a()
Right contains 2 more items, first extra item: call.mock_func2b()


I suspect it may be due to the order in which the mocks are applied. In particular, I think this is due to the fact that I am mocking a function that import another function, while also mocking this function simultaneously.

Has anyone run into this issue before and can explain why this might be happening?

Thanks!

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