tidy up test init

src/utils/test.ts

@@ -122,8 +122,15 @@ export function mockMembership(
 // Maybe it'd be good to move this to matrix-js-sdk? Our testing needs are
 // rather simple, but if one util to mock a member is good enough for us, maybe
 // it's useful for matrix-js-sdk consumers in general.
-export function mockRoomMember(member: Partial<RoomMember>): RoomMember {
-  return { ...mockEmitter(), ...member } as RoomMember;
+export function mockRoomMember(
+  rtcMembership: CallMembership,
+  member: Partial<RoomMember> = {},
+): RoomMember {
+  return {
+    ...mockEmitter(),
+    userId: rtcMembership.sender,
+    ...member,
+  } as RoomMember;
 }
 
 export function mockMatrixRoom(room: Partial<MatrixRoom>): MatrixRoom {