Update knock test utilities to be more generic/useful (#758)

They now match the style of the other utilities under `client`: `mustKnockOnRoomSynced`/`syncKnockedOn`

This is spawning from trying to write some knock tests that also stressed element-hq/synapse#18075 but they didn't pan out. I thought this refactor and update was still useful to upstream in any case.

tests/knocking_test.go

@@ -117,11 +117,11 @@ func knockingBetweenTwoUsersTest(t *testing.T, roomID string, inRoomUser, knocki
 	})
 
 	t.Run("Knocking on a room with join rule 'knock' should succeed", func(t *testing.T) {
-		knockOnRoomSynced(t, knockingUser, roomID, testKnockReason, []string{"hs1"})
+		mustKnockOnRoomSynced(t, knockingUser, roomID, testKnockReason, []string{"hs1"})
 	})
 
 	t.Run("A user that has already knocked is allowed to knock again on the same room", func(t *testing.T) {
-		knockOnRoomSynced(t, knockingUser, roomID, "I really like knock knock jokes", []string{"hs1"})
+		mustKnockOnRoomSynced(t, knockingUser, roomID, "I really like knock knock jokes", []string{"hs1"})
 	})
 
 	t.Run("Users in the room see a user's membership update when they knock", func(t *testing.T) {
@@ -183,7 +183,7 @@ func knockingBetweenTwoUsersTest(t *testing.T, roomID string, inRoomUser, knocki
 			})
 
 			// Knock again to return us to the knocked state
-			knockOnRoomSynced(t, knockingUser, roomID, "Let me in... again?", []string{"hs1"})
+			mustKnockOnRoomSynced(t, knockingUser, roomID, "Let me in... again?", []string{"hs1"})
 		})
 	}
 
@@ -211,7 +211,7 @@ func knockingBetweenTwoUsersTest(t *testing.T, roomID string, inRoomUser, knocki
 		}))
 
 		// Knock again
-		knockOnRoomSynced(t, knockingUser, roomID, "Pleeease let me in?", []string{"hs1"})
+		mustKnockOnRoomSynced(t, knockingUser, roomID, "Pleeease let me in?", []string{"hs1"})
 	})
 
 	t.Run("A user can knock on a room without a reason", func(t *testing.T) {
@@ -227,7 +227,7 @@ func knockingBetweenTwoUsersTest(t *testing.T, roomID string, inRoomUser, knocki
 		)
 
 		// Knock again, this time without a reason
-		knockOnRoomSynced(t, knockingUser, roomID, "", []string{"hs1"})
+		mustKnockOnRoomSynced(t, knockingUser, roomID, "", []string{"hs1"})
 	})
 
 	t.Run("A user in the room can accept a knock", func(t *testing.T) {
@@ -279,22 +279,36 @@ func knockingBetweenTwoUsersTest(t *testing.T, roomID string, inRoomUser, knocki
 	})
 }
 
-// knockOnRoomSynced will knock on a given room on the behalf of a user, and block until the knock has persisted.
+func syncKnockedOn(userID, roomID string) client.SyncCheckOpt {
+	return func(clientUserID string, topLevelSyncJSON gjson.Result) error {
+		// two forms which depend on what the client user is:
+		// - passively viewing a membership for a room you're joined in
+		// - actively leaving the room
+		if clientUserID == userID {
+			events := topLevelSyncJSON.Get("rooms.knock." + client.GjsonEscape(roomID) + ".knock_state.events")
+			if events.Exists() && events.IsArray() {
+				// We don't currently define any required state event types to be sent.
+				// If we've reached this point, then an entry for this room was found
+				return nil
+			}
+			return fmt.Errorf("no knock section for room %s", roomID)
+		}
+
+		// passive
+		return client.SyncTimelineHas(roomID, func(ev gjson.Result) bool {
+			return ev.Get("type").Str == "m.room.member" && ev.Get("state_key").Str == userID && ev.Get("content.membership").Str == "knock"
+		})(clientUserID, topLevelSyncJSON)
+	}
+}
+
+// mustKnockOnRoomSynced will knock on a given room on the behalf of a user, and block until the knock has persisted.
 // serverNames should be populated if knocking on a room that the user's homeserver isn't currently a part of.
 // Fails the test if the knock response does not return a 200 status code.
-func knockOnRoomSynced(t *testing.T, c *client.CSAPI, roomID, reason string, serverNames []string) {
+func mustKnockOnRoomSynced(t *testing.T, c *client.CSAPI, roomID, reason string, serverNames []string) {
 	knockOnRoomWithStatus(t, c, roomID, reason, serverNames, 200)
 
 	// The knock should have succeeded. Block until we see the knock appear down sync
-	c.MustSyncUntil(t, client.SyncReq{}, func(clientUserID string, topLevelSyncJSON gjson.Result) error {
-		events := topLevelSyncJSON.Get("rooms.knock." + client.GjsonEscape(roomID) + ".knock_state.events")
-		if events.Exists() && events.IsArray() {
-			// We don't currently define any required state event types to be sent.
-			// If we've reached this point, then an entry for this room was found
-			return nil
-		}
-		return fmt.Errorf("no knock section for room %s", roomID)
-	})
+	c.MustSyncUntil(t, client.SyncReq{}, syncKnockedOn(c.UserID, roomID))
 }
 
 // knockOnRoomWithStatus will knock on a given room on the behalf of a user.