Round out tests

tests/storage/test_sliding_sync_tables.py

@@ -4373,16 +4373,6 @@ class SlidingSyncTablesCatchUpBackgroundUpdatesTestCase(SlidingSyncTablesTestCas
         # `SlidingSyncTablesBackgroundUpdatesTestCase` to cover that logic.
         room_id = self.helper.create_room_as(user1_id, tok=user1_tok)
 
-        # Get a snapshot of the `sliding_sync_joined_rooms` table before we add some state
-        sliding_sync_joined_rooms_results_before_state = (
-            self._get_sliding_sync_joined_rooms()
-        )
-        self.assertIncludes(
-            set(sliding_sync_joined_rooms_results_before_state.keys()),
-            {room_id},
-            exact=True,
-        )
-
         # Make sure all of the background updates have finished before we start the
         # catch-up. Even though it should work fine if the other background update is
         # still running, we want to see the catch-up routine restore the progress
@@ -4561,7 +4551,6 @@ class SlidingSyncTablesCatchUpBackgroundUpdatesTestCase(SlidingSyncTablesTestCas
         `sliding_sync_membership_snapshots` stale) will be caught when Synapse is upgraded and
         the catch-up routine is run.
         """
-
         user1_id = self.register_user("user1", "pass")
         user1_tok = self.login(user1_id, "pass")
         user2_id = self.register_user("user2", "pass")
@@ -4696,6 +4685,93 @@ class SlidingSyncTablesCatchUpBackgroundUpdatesTestCase(SlidingSyncTablesTestCas
         self,
     ) -> None:
         """
-        TODO
+        Test that if you start your homeserver with no rooms on a Synapse version that
+        supports the sliding sync tables and the historical background update completes
+        (because no rooms/membership to process), then Synapse is downgraded and new
+        rooms are created/joined; when Synapse is upgraded, the rooms will be processed
+        catch-up routine is run.
         """
-        TODO
+        user1_id = self.register_user("user1", "pass")
+        user1_tok = self.login(user1_id, "pass")
+        user2_id = self.register_user("user2", "pass")
+        user2_tok = self.login(user2_id, "pass")
+
+        # Instead of testing with various levels of room state that should appear in the
+        # table, we're only using one room to keep this test simple. Because the
+        # underlying background update to populate these tables is the same as this
+        # catch-up routine, we are going to rely on
+        # `SlidingSyncTablesBackgroundUpdatesTestCase` to cover that logic.
+        room_id = self.helper.create_room_as(user1_id, tok=user1_tok)
+        # User2 joins the room
+        self.helper.join(room_id, user2_id, tok=user2_tok)
+
+        # Make sure all of the background updates have finished before we start the
+        # catch-up. Even though it should work fine if the other background update is
+        # still running, we want to see the catch-up routine restore the progress
+        # correctly.
+        #
+        # We also don't want the normal background update messing with our results so we
+        # run this before we do our manual database clean-up to simulate new events
+        # being sent while Synapse was downgraded.
+        self.wait_for_background_updates()
+
+        # Rollback the `sliding_sync_membership_snapshots` table as if the user2
+        # membership never made it into the table. This is to simulate a membership
+        # change while Synapse was downgraded.
+        self.get_success(
+            self.store.db_pool.simple_delete_many(
+                table="sliding_sync_membership_snapshots",
+                column="room_id",
+                iterable=(room_id,),
+                keyvalues={},
+                desc="simulate room being created while Synapse was downgraded",
+            )
+        )
+
+        # We shouldn't find anything in the table because we just deleted them in
+        # preparation for the test.
+        sliding_sync_membership_snapshots_results = (
+            self._get_sliding_sync_membership_snapshots()
+        )
+        self.assertIncludes(
+            set(sliding_sync_membership_snapshots_results.keys()),
+            set(),
+            exact=True,
+        )
+
+        # The function under test. It should clear out stale data and start the
+        # background update to catch-up on the missing data.
+        self.get_success(
+            self.store.db_pool.runInteraction(
+                "_resolve_stale_data_in_sliding_sync_membership_snapshots_table",
+                _resolve_stale_data_in_sliding_sync_membership_snapshots_table,
+            )
+        )
+
+        # We still shouldn't find any data yet
+        sliding_sync_membership_snapshots_results = (
+            self._get_sliding_sync_membership_snapshots()
+        )
+        self.assertIncludes(
+            set(sliding_sync_membership_snapshots_results.keys()),
+            set(),
+            exact=True,
+        )
+
+        # Wait for the catch-up background update to finish
+        self.store.db_pool.updates._all_done = False
+        self.wait_for_background_updates()
+
+        # Ensure that the table is populated correctly after the catch-up background
+        # update finishes
+        sliding_sync_membership_snapshots_results = (
+            self._get_sliding_sync_membership_snapshots()
+        )
+        self.assertIncludes(
+            set(sliding_sync_membership_snapshots_results.keys()),
+            {
+                (room_id, user1_id),
+                (room_id, user2_id),
+            },
+            exact=True,
+        )