code: function getSyncResponse(roomMembers) {
      const stateEvents = [
          testUtils.mkEvent({
              type: 'm.room.encryption',
              skey: '',
              content: {
                  algorithm: 'm.megolm.v1.aes-sha2',
              },
          }),
      ];
  
      Array.prototype.push.apply(
          stateEvents,
          roomMembers.map(
              (m) => testUtils.mkMembership({
                  mship: 'join',
                  sender: m,
              }),
          ),
      );
  
      const syncResponse = {
          next_batch: 1,
          rooms: {
              join: {
                  [ROOM_ID]: {
                      state: {
                          events: stateEvents,
                      },
                  },
              },
          },
      };
  
      return syncResponse;
  }
docs: get a /sync response which contains a single e2e room (ROOM_ID), with the
  members given
  
  @param {string[]} roomMembers
  
  @return {object} sync response