Add test to reflect desired behavior

tests/storage/test_purge.py

@@ -122,3 +122,89 @@ def test_purge_room(self) -> None:
         self.store._invalidate_local_get_event_cache(create_event.event_id)
         self.get_failure(self.store.get_event(create_event.event_id), NotFoundError)
         self.get_failure(self.store.get_event(first["event_id"]), NotFoundError)
+
+    def test_purge_one_room_will_not_uncache_events_from_another(self) -> None:
+        """
+        Purging a room will delete everything about it, but leave other rooms still in
+        the event cache.
+        """
+        # Create a second room to use for our testing. This room will have four messages
+        # as well, but they should stay in the get_event_cache
+        self.room_id2 = self.helper.create_room_as(self.user_id)
+
+        # Send four messages to the first room
+        r1_first = self.helper.send(self.room_id, body="test1")
+        r1_second = self.helper.send(self.room_id, body="test2")
+        r1_third = self.helper.send(self.room_id, body="test3")
+        r1_last = self.helper.send(self.room_id, body="test4")
+
+        # Send four messages to the second room
+        r2_first = self.helper.send(self.room_id2, body="test1_2")
+        r2_second = self.helper.send(self.room_id2, body="test2_2")
+        r2_third = self.helper.send(self.room_id2, body="test3_2")
+        r2_last = self.helper.send(self.room_id2, body="test4_2")
+
+        # Get the current room state for the first room(the one that will be deleted).
+        create_event = self.get_success(
+            self._storage_controllers.state.get_current_state_event(
+                self.room_id, "m.room.create", ""
+            )
+        )
+        assert create_event is not None
+
+        # Purge everything before this topological token
+        self.get_success(
+            self._storage_controllers.purge_events.purge_room(self.room_id)
+        )
+
+        # The room has been purged, the appropriate invalidations should be done.
+        # The events from the first room should not be in the event cache.
+        # Note: the function to call retrieves a Dict[str, EventCacheEntry], if the Dict
+        # is empty this is successful.
+        self.assertDictEqual(
+            self.store._get_events_from_local_cache(r1_first["event_id"]),
+            {},
+            f"Event found in cache: {r1_first}",
+        )
+        self.assertDictEqual(
+            self.store._get_events_from_local_cache(r1_second["event_id"]),
+            {},
+            f"Event found in cache: {r1_second}",
+        )
+        self.assertDictEqual(
+            self.store._get_events_from_local_cache(r1_third["event_id"]),
+            {},
+            f"Event found in cache: {r1_third}",
+        )
+        self.assertDictEqual(
+            self.store._get_events_from_local_cache(r1_last["event_id"]),
+            {},
+            f"Event found in cache: {r1_last}",
+        )
+
+        # The events from the second room should still be in the event cache. If the
+        # Dict retrieved has anything and isn't empty, this is a success. Might want to
+        # change this to check for a instance of class EventCacheEntry instead.
+        self.assertIsNot(
+            self.store._get_events_from_local_cache(r2_first["event_id"]),
+            {},
+            f"Event found in cache: {r2_first}",
+        )
+        self.assertIsNot(
+            self.store._get_events_from_local_cache(r2_second["event_id"]),
+            {},
+            f"Event found in cache: {r2_second}",
+        )
+        self.assertIsNot(
+            self.store._get_events_from_local_cache(r2_third["event_id"]),
+            {},
+            f"Event found in cache: {r2_third}",
+        )
+        self.assertIsNot(
+            self.store._get_events_from_local_cache(r2_last["event_id"]),
+            {},
+            f"Event found in cache: {r2_last}",
+        )
+
+        self.get_failure(self.store.get_event(create_event.event_id), NotFoundError)
+        self.get_failure(self.store.get_event(r1_first["event_id"]), NotFoundError)