Fix regression with mocker.patch not being undone correctly

The problem was introduced due to a bug in #417 which escaped review: we should always add a mock object to the cache, even if a similar one already exists.

Fix #420

CHANGELOG.rst

@@ -6,6 +6,8 @@ UNRELEASED
 
 * `#415 <https://github.com/pytest-dev/pytest-mock/pull/415>`_: ``MockType`` and ``AsyncMockType`` can be imported from ``pytest_mock`` for type annotation purposes.
 
+* `#420 <https://github.com/pytest-dev/pytest-mock/issues/420>`_: Fixed a regression which would cause ``mocker.patch.object`` to not being properly cleared between tests.
+
 
 3.13.0 (2024-03-21)
 -------------------

src/pytest_mock/plugin.py

@@ -60,11 +60,8 @@ def find(self, mock: MockType) -> MockCacheItem:
         return the_mock
 
     def add(self, mock: MockType, **kwargs: Any) -> MockCacheItem:
-        try:
-            return self.find(mock)
-        except ValueError:
-            self.cache.append(MockCacheItem(mock=mock, **kwargs))
-            return self.cache[-1]
+        self.cache.append(MockCacheItem(mock=mock, **kwargs))
+        return self.cache[-1]
 
     def remove(self, mock: MockType) -> None:
         mock_item = self.find(mock)

tests/test_pytest_mock.py

@@ -1264,3 +1264,28 @@ def foo(self):
     mocker.stop(spy)
     assert un_spy.foo() == 42
     assert spy.call_count == 1
+
+
+def test_stop_multiple_patches(mocker: MockerFixture) -> None:
+    """Regression for #420."""
+
+    class Class1:
+        @staticmethod
+        def get():
+            return 1
+
+    class Class2:
+        @staticmethod
+        def get():
+            return 2
+
+    def handle_get():
+        return 3
+
+    mocker.patch.object(Class1, "get", handle_get)
+    mocker.patch.object(Class2, "get", handle_get)
+
+    mocker.stopall()
+
+    assert Class1.get() == 1
+    assert Class2.get() == 2