Track return value of spied functions (#155)

Related to #118

Author: nicoddemus

CHANGELOG.rst

@@ -1,3 +1,9 @@
+1.11.0
+------
+
+* The object returned by ``mocker.spy`` now also tracks the return value
+  of the spied method/function.
+
 1.10.4
 ------
 

README.rst

@@ -85,10 +85,9 @@ These objects from the ``mock`` module are accessible directly from ``mocker`` f
 Spy
 ---
 
-The spy acts exactly like the original method in all cases, except it allows use of `mock`
+The spy acts exactly like the original method in all cases, except it allows use of ``mock``
 features with it, like retrieving call count. It also works for class and static methods.
 
-
 .. code-block:: python
 
     def test_spy(mocker):
@@ -101,6 +100,9 @@ features with it, like retrieving call count. It also works for class and static
         assert foo.bar() == 42
         assert foo.bar.call_count == 1
 
+Since version ``1.11``, it is also possible to query the ``return_value`` attribute
+to observe what the spied function/method returned.
+
 Stub
 ----
 

pytest_mock.py

@@ -2,6 +2,7 @@
 
 import inspect
 import sys
+from functools import wraps
 
 import pytest
 
@@ -104,7 +105,13 @@ def spy(self, obj, name):
                 if isinstance(value, (classmethod, staticmethod)):
                     autospec = False
 
-        result = self.patch.object(obj, name, side_effect=method, autospec=autospec)
+        @wraps(method)
+        def wrapper(*args, **kwargs):
+            r = method(*args, **kwargs)
+            result.return_value = r
+            return r
+
+        result = self.patch.object(obj, name, side_effect=wrapper, autospec=autospec)
         return result
 
     def stub(self, name=None):

test_pytest_mock.py

@@ -238,7 +238,9 @@ def bar(self, arg):
     assert foo.bar(arg=10) == 20
     assert other.bar(arg=10) == 20
     foo.bar.assert_called_once_with(arg=10)
+    assert foo.bar.return_value == 20
     spy.assert_called_once_with(arg=10)
+    assert spy.return_value == 20
 
 
 @skip_pypy
@@ -272,6 +274,7 @@ class Foo(Base):
     assert other.bar(arg=10) == 20
     calls = [mocker.call(foo, arg=10), mocker.call(other, arg=10)]
     assert spy.call_args_list == calls
+    assert spy.return_value == 20
 
 
 @skip_pypy
@@ -284,7 +287,9 @@ def bar(cls, arg):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
+    assert Foo.bar.return_value == 20
     spy.assert_called_once_with(arg=10)
+    assert spy.return_value == 20
 
 
 @skip_pypy
@@ -301,7 +306,9 @@ class Foo(Base):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
+    assert Foo.bar.return_value == 20
     spy.assert_called_once_with(arg=10)
+    assert spy.return_value == 20
 
 
 @skip_pypy
@@ -320,7 +327,9 @@ def bar(cls, arg):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
+    assert Foo.bar.return_value == 20
     spy.assert_called_once_with(arg=10)
+    assert spy.return_value == 20
 
 
 @skip_pypy
@@ -333,7 +342,9 @@ def bar(arg):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
+    assert Foo.bar.return_value == 20
     spy.assert_called_once_with(arg=10)
+    assert spy.return_value == 20
 
 
 @skip_pypy
@@ -350,7 +361,9 @@ class Foo(Base):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
+    assert Foo.bar.return_value == 20
     spy.assert_called_once_with(arg=10)
+    assert spy.return_value == 20
 
 
 @contextmanager