Spy exceptions

CHANGELOG.rst

@@ -1,3 +1,9 @@
+1.13.0
+------
+
+* The object returned by ``mocker.spy`` now also tracks any side effect
+  of the spied method/function.
+
 1.12.1 (2019-11-20)
 -------------------
 

README.rst

@@ -103,6 +103,9 @@ features with it, like retrieving call count. It also works for class and static
 Since version ``1.11``, it is also possible to query the ``return_value`` attribute
 to observe what the spied function/method returned.
 
+Since version ``1.13``, it is also possible to query the ``side_effect`` attribute
+to observe any exception thrown by the spied function/method.
+
 Stub
 ----
 

src/pytest_mock/plugin.py

@@ -113,8 +113,13 @@ def spy(self, obj, name):
 
         @w
         def wrapper(*args, **kwargs):
-            r = method(*args, **kwargs)
-            result.return_value = r
+            try:
+                r = method(*args, **kwargs)
+            except Exception as e:
+                result.side_effect = e
+                raise
+            else:
+                result.return_value = r
             return r
 
         result = self.patch.object(obj, name, side_effect=wrapper, autospec=autospec)

tests/test_pytest_mock.py

@@ -243,6 +243,25 @@ def bar(self, arg):
     assert spy.return_value == 20
 
 
+def test_instance_method_spy_exception(mocker):
+    excepted_message = "foo"
+
+    class Foo(object):
+        def bar(self, arg):
+            raise Exception(excepted_message)
+
+    foo = Foo()
+    other = Foo()
+    spy = mocker.spy(foo, "bar")
+
+    with pytest.raises(Exception) as exc_info:
+        foo.bar(10)
+    assert str(exc_info.value) == excepted_message
+
+    foo.bar.assert_called_once_with(arg=10)
+    assert spy.side_effect == exc_info.value
+
+
 @skip_pypy
 def test_instance_method_by_class_spy(mocker):
     class Foo(object):