Stop patching EventBase.__eq__ in tests. (#16349)

It is clearer to directly test equality instead of doing indirect
assertions via patching __eq__.

changelog.d/16349.misc

@@ -0,0 +1 @@
+Avoid patching code in tests.

tests/replication/storage/_base.py

@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Iterable, Optional
+from typing import Any, Callable, Iterable, Optional
 from unittest.mock import Mock
 
 from twisted.test.proto_helpers import MemoryReactor
@@ -47,24 +47,31 @@ class BaseWorkerStoreTestCase(BaseStreamTestCase):
         self.pump(0.1)
 
     def check(
-        self, method: str, args: Iterable[Any], expected_result: Optional[Any] = None
+        self,
+        method: str,
+        args: Iterable[Any],
+        expected_result: Optional[Any] = None,
+        asserter: Optional[Callable[[Any, Any, Optional[Any]], None]] = None,
     ) -> None:
+        if asserter is None:
+            asserter = self.assertEqual
+
         master_result = self.get_success(getattr(self.master_store, method)(*args))
         worker_result = self.get_success(getattr(self.worker_store, method)(*args))
         if expected_result is not None:
-            self.assertEqual(
+            asserter(
                 master_result,
                 expected_result,
                 "Expected master result to be %r but was %r"
                 % (expected_result, master_result),
             )
-            self.assertEqual(
+            asserter(
                 worker_result,
                 expected_result,
                 "Expected worker result to be %r but was %r"
                 % (expected_result, worker_result),
             )
-        self.assertEqual(
+        asserter(
             master_result,
             worker_result,
             "Worker result %r does not match master result %r"

tests/replication/storage/test_events.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import Any, Callable, Iterable, List, Optional, Tuple
+from typing import Any, Iterable, List, Optional, Tuple
 
 from canonicaljson import encode_canonical_json
 from parameterized import parameterized
@@ -21,7 +21,7 @@ from twisted.test.proto_helpers import MemoryReactor
 
 from synapse.api.constants import ReceiptTypes
 from synapse.api.room_versions import RoomVersions
-from synapse.events import EventBase, _EventInternalMetadata, make_event_from_dict
+from synapse.events import EventBase, make_event_from_dict
 from synapse.events.snapshot import EventContext
 from synapse.handlers.room import RoomEventSource
 from synapse.server import HomeServer
@@ -46,32 +46,9 @@ ROOM_ID = "!room:test"
 logger = logging.getLogger(__name__)
 
 
-def dict_equals(self: EventBase, other: EventBase) -> bool:
-    me = encode_canonical_json(self.get_pdu_json())
-    them = encode_canonical_json(other.get_pdu_json())
-    return me == them
-
-
-def patch__eq__(cls: object) -> Callable[[], None]:
-    eq = getattr(cls, "__eq__", None)
-    cls.__eq__ = dict_equals  # type: ignore[assignment]
-
-    def unpatch() -> None:
-        if eq is not None:
-            cls.__eq__ = eq  # type: ignore[method-assign]
-
-    return unpatch
-
-
 class EventsWorkerStoreTestCase(BaseWorkerStoreTestCase):
     STORE_TYPE = EventsWorkerStore
 
-    def setUp(self) -> None:
-        # Patch up the equality operator for events so that we can check
-        # whether lists of events match using assertEqual
-        self.unpatches = [patch__eq__(_EventInternalMetadata), patch__eq__(EventBase)]
-        super().setUp()
-
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         super().prepare(reactor, clock, hs)
 
@@ -84,8 +61,14 @@ class EventsWorkerStoreTestCase(BaseWorkerStoreTestCase):
             )
         )
 
-    def tearDown(self) -> None:
+    def assertEventsEqual(
-        [unpatch() for unpatch in self.unpatches]
+        self, first: EventBase, second: EventBase, msg: Optional[Any] = None
+    ) -> None:
+        self.assertEqual(
+            encode_canonical_json(first.get_pdu_json()),
+            encode_canonical_json(second.get_pdu_json()),
+            msg,
+        )
 
     def test_get_latest_event_ids_in_room(self) -> None:
         create = self.persist(type="m.room.create", key="", creator=USER_ID)
@@ -107,7 +90,7 @@ class EventsWorkerStoreTestCase(BaseWorkerStoreTestCase):
 
         msg = self.persist(type="m.room.message", msgtype="m.text", body="Hello")
         self.replicate()
-        self.check("get_event", [msg.event_id], msg)
+        self.check("get_event", [msg.event_id], msg, asserter=self.assertEventsEqual)
 
         redaction = self.persist(type="m.room.redaction", redacts=msg.event_id)
         self.replicate()
@@ -119,7 +102,9 @@ class EventsWorkerStoreTestCase(BaseWorkerStoreTestCase):
         redacted = make_event_from_dict(
             msg_dict, internal_metadata_dict=msg.internal_metadata.get_dict()
         )
-        self.check("get_event", [msg.event_id], redacted)
+        self.check(
+            "get_event", [msg.event_id], redacted, asserter=self.assertEventsEqual
+        )
 
     def test_backfilled_redactions(self) -> None:
         self.persist(type="m.room.create", key="", creator=USER_ID)
@@ -127,7 +112,7 @@ class EventsWorkerStoreTestCase(BaseWorkerStoreTestCase):
 
         msg = self.persist(type="m.room.message", msgtype="m.text", body="Hello")
         self.replicate()
-        self.check("get_event", [msg.event_id], msg)
+        self.check("get_event", [msg.event_id], msg, asserter=self.assertEventsEqual)
 
         redaction = self.persist(
             type="m.room.redaction", redacts=msg.event_id, backfill=True
@@ -141,7 +126,9 @@ class EventsWorkerStoreTestCase(BaseWorkerStoreTestCase):
         redacted = make_event_from_dict(
             msg_dict, internal_metadata_dict=msg.internal_metadata.get_dict()
         )
-        self.check("get_event", [msg.event_id], redacted)
+        self.check(
+            "get_event", [msg.event_id], redacted, asserter=self.assertEventsEqual
+        )
 
     def test_invites(self) -> None:
         self.persist(type="m.room.create", key="", creator=USER_ID)