Wire local room logic (#9078)

* Wire local room logic

* Migrate to testling-lib; update test descriptions

src/utils/localRoom/isLocalRoom.ts

@@ -0,0 +1,26 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { Room } from "matrix-js-sdk/src/matrix";
+
+import { LocalRoom, LOCAL_ROOM_ID_PREFIX } from "../../models/LocalRoom";
+
+export function isLocalRoom(roomOrID: Room|string): boolean {
+    if (typeof roomOrID === "string") {
+        return roomOrID.startsWith(LOCAL_ROOM_ID_PREFIX);
+    }
+    return roomOrID instanceof LocalRoom;
+}