Fix #178: handle spy on async functions

Author: frankie567

setup.py

@@ -19,7 +19,7 @@
     description="Thin-wrapper around the mock package for easier use with pytest",
     long_description=open("README.rst", encoding="utf-8").read(),
     keywords="pytest mock",
-    extras_require={"dev": ["pre-commit", "tox"]},
+    extras_require={"dev": ["pre-commit", "tox", "pytest-asyncio"]},
     classifiers=[
         "Development Status :: 5 - Production/Stable",
         "Framework :: Pytest",

src/pytest_mock/plugin.py

@@ -1,3 +1,4 @@
+import asyncio
 import functools
 import inspect
 
@@ -96,7 +97,6 @@ def spy(self, obj, name):
                 if isinstance(value, (classmethod, staticmethod)):
                     autospec = False
 
-        @functools.wraps(method)
         def wrapper(*args, **kwargs):
             spy_obj.spy_return = None
             spy_obj.spy_exception = None
@@ -109,7 +109,24 @@ def wrapper(*args, **kwargs):
                 spy_obj.spy_return = r
             return r
 
-        spy_obj = self.patch.object(obj, name, side_effect=wrapper, autospec=autospec)
+        async def async_wrapper(*args, **kwargs):
+            spy_obj.spy_return = None
+            spy_obj.spy_exception = None
+            try:
+                r = await method(*args, **kwargs)
+            except Exception as e:
+                spy_obj.spy_exception = e
+                raise
+            else:
+                spy_obj.spy_return = r
+            return r
+
+        if asyncio.iscoroutinefunction(method):
+            wrapped = functools.update_wrapper(async_wrapper, method)
+        else:
+            wrapped = functools.update_wrapper(wrapper, method)
+
+        spy_obj = self.patch.object(obj, name, side_effect=wrapped, autospec=autospec)
         spy_obj.spy_return = None
         spy_obj.spy_exception = None
         return spy_obj

tests/test_pytest_mock.py

@@ -405,6 +405,21 @@ def __call__(self, x):
     assert spy.spy_return == 20
 
 
+@pytest.mark.asyncio
+async def test_instance_async_method_spy(mocker):
+    class Foo:
+        async def bar(self, arg):
+            return arg * 2
+
+    foo = Foo()
+    spy = mocker.spy(foo, "bar")
+
+    result = await foo.bar(10)
+
+    spy.assert_called_once_with(10)
+    assert result == 20
+
+
 @contextmanager
 def assert_traceback():
     """

tox.ini

@@ -5,6 +5,7 @@ envlist = py{35,36,37,38}, linting, norewrite
 passenv = USER USERNAME
 deps =
     coverage
+    pytest-asyncio
 commands =
     coverage run --append --source={envsitepackagesdir}/pytest_mock -m pytest tests