Spy with async function not registering calls until coroutine is awaited

Started happening after I upgraded to Python version 3.13.
Pytest mock version 3.14.1

AsyncMock is only registering calls after the coroutine is awaited, when it should do it when the function is called.

Code to reproduce

File tests/other_module.py

async def a(value):
    return value * 2

File tests/test_1.py

from unittest.mock import AsyncMock

import pytest

import other_module

pytestmark = pytest.mark.asyncio(loop_scope="session")


def b(value):
    return other_module.a(value)


async def test_1(mocker):
    a_spy: AsyncMock = mocker.spy(other_module, "a")
    result = b(10)

    assert not a_spy.called  # This should be True because 'a' was called, but it's False

    await result
    assert a_spy.called  # Now it's True

Expected result: a_spy.called should return True even if the coroutine was not awaited.

I could not reproduce the behavior using unittest's patch.

    async def test_1():
        with patch("other_module.a") as a_spy:
            result = b(10)
    
>           assert not a_spy.called  # This should be True because 'a' was called, but it's False
            ^^^^^^^^^^^^^^^^^^^^^^^
E           AssertionError: assert not True
E            +  where True = <AsyncMock name='a' id='139651671861504'>.called

tests/test_1.py:18: AssertionError

@GabrielSalla

Thanks @GabrielSalla for the report!

I'm short on time to investigate this now, but here is the relevant code if somebody wants to investigate:

pytest-mock/src/pytest_mock/plugin.py

Lines 161 to 209 in ba83a70

    
               def spy(self, obj: object, name: str) -> MockType: 
        
                   """ 
        
                   Create a spy of method. It will run method normally, but it is now 
        
                   possible to use `mock` call features with it, like call count. 
        
                   :param obj: An object. 
        
                   :param name: A method in object. 
        
                   :return: Spy object. 
        
                   """ 
        
                   method = getattr(obj, name) 
        
                   def wrapper(*args, **kwargs): 
        
                       spy_obj.spy_return = None 
        
                       spy_obj.spy_exception = None 
        
                       try: 
        
                           r = method(*args, **kwargs) 
        
                       except BaseException as e: 
        
                           spy_obj.spy_exception = e 
        
                           raise 
        
                       else: 
        
                           spy_obj.spy_return = r 
        
                           spy_obj.spy_return_list.append(r) 
        
                       return r 
        
                   async def async_wrapper(*args, **kwargs): 
        
                       spy_obj.spy_return = None 
        
                       spy_obj.spy_exception = None 
        
                       try: 
        
                           r = await method(*args, **kwargs) 
        
                       except BaseException as e: 
        
                           spy_obj.spy_exception = e 
        
                           raise 
        
                       else: 
        
                           spy_obj.spy_return = r 
        
                           spy_obj.spy_return_list.append(r) 
        
                       return r 
        
                   if inspect.iscoroutinefunction(method): 
        
                       wrapped = functools.update_wrapper(async_wrapper, method) 
        
                   else: 
        
                       wrapped = functools.update_wrapper(wrapper, method) 
        
                   autospec = inspect.ismethod(method) or inspect.isfunction(method) 
        
                   spy_obj = self.patch.object(obj, name, side_effect=wrapped, autospec=autospec) 
        
                   spy_obj.spy_return = None 
        
                   spy_obj.spy_return_list = [] 
        
                   spy_obj.spy_exception = None 
        
                   return spy_obj

I'll take a look at it and see if I can find out what's happening

Digging with the debugger, I was able to narrow down the problem to the autospec parameter.

Using unittest's patch.object with autospec=True (which is the same value when using spy) I'm able to reproduce the same behavior. I'll dig deeper to understand this parameter.

Edit: I think it's a Python bug, not pytest-mock's.

Edit 2: I've opened a bug on cpython python/cpython#137594

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Spy with async function not registering calls until coroutine is awaited #519

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	def spy(self, obj: object, name: str) -> MockType:
	"""
	Create a spy of method. It will run method normally, but it is now
	possible to use `mock` call features with it, like call count.

	:param obj: An object.
	:param name: A method in object.
	:return: Spy object.
	"""
	method = getattr(obj, name)

	def wrapper(args, *kwargs):
	spy_obj.spy_return = None
	spy_obj.spy_exception = None
	try:
	r = method(args, *kwargs)
	except BaseException as e:
	spy_obj.spy_exception = e
	raise
	else:
	spy_obj.spy_return = r
	spy_obj.spy_return_list.append(r)
	return r

	async def async_wrapper(args, *kwargs):
	spy_obj.spy_return = None
	spy_obj.spy_exception = None
	try:
	r = await method(args, *kwargs)
	except BaseException as e:
	spy_obj.spy_exception = e
	raise
	else:
	spy_obj.spy_return = r
	spy_obj.spy_return_list.append(r)
	return r

	if inspect.iscoroutinefunction(method):
	wrapped = functools.update_wrapper(async_wrapper, method)
	else:
	wrapped = functools.update_wrapper(wrapper, method)

	autospec = inspect.ismethod(method) or inspect.isfunction(method)

	spy_obj = self.patch.object(obj, name, side_effect=wrapped, autospec=autospec)
	spy_obj.spy_return = None
	spy_obj.spy_return_list = []
	spy_obj.spy_exception = None
	return spy_obj

Spy with async function not registering calls until coroutine is awaited #519

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nicoddemus commented on Aug 9, 2025

GabrielSalla commented on Aug 9, 2025

GabrielSalla commented on Aug 9, 2025

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