diff --git a/src/state/CallViewModel.test.ts b/src/state/CallViewModel.test.ts
index 9f208112..5af59711 100644
--- a/src/state/CallViewModel.test.ts
+++ b/src/state/CallViewModel.test.ts
@@ -24,11 +24,7 @@ import {
 } from "livekit-client";
 import * as ComponentsCore from "@livekit/components-core";
 import { isEqual } from "lodash";
-import {
-  CallMembership,
-  MatrixRTCSession,
-  MatrixRTCSessionEvent,
-} from "matrix-js-sdk/src/matrixrtc";
+import { CallMembership, MatrixRTCSession } from "matrix-js-sdk/src/matrixrtc";
 
 import { CallViewModel, Layout } from "./CallViewModel";
 import {
@@ -39,13 +35,13 @@ import {
   mockRemoteParticipant,
   withTestScheduler,
   mockMembership,
+  MockRTCSession,
 } from "../utils/test";
 import {
   ECAddonConnectionState,
   ECConnectionState,
 } from "../livekit/useECConnectionState";
 import { E2eeType } from "../e2ee/e2eeType";
-import { MockRoom, MockRTCSession } from "../useReactions.test";
 
 vi.mock("@livekit/components-core");
 
@@ -199,12 +195,11 @@ function withCallViewModel(
     } as Partial<MatrixClient> as MatrixClient,
     getMember: (userId) => roomMembers.get(userId) ?? null,
   });
-  const rtcSession = new MockRTCSession(room as unknown as MockRoom);
-  rtcMembers.subscribe((m) => {
-    // always prepend the local participant
-    rtcSession.memberships = [localRtcMember, ...m];
-    rtcSession.emit(MatrixRTCSessionEvent.MembershipsChanged);
-  });
+  const rtcSession = new MockRTCSession(
+    room,
+    localRtcMember,
+    [],
+  ).withMemberships(rtcMembers);
   const participantsSpy = vi
     .spyOn(ComponentsCore, "connectedParticipantsObserver")
     .mockReturnValue(remoteParticipants);
diff --git a/src/utils/test.ts b/src/utils/test.ts
index c6789a41..68971bbe 100644
--- a/src/utils/test.ts
+++ b/src/utils/test.ts
@@ -11,10 +11,14 @@ import {
   RoomMember,
   Room as MatrixRoom,
   MatrixEvent,
+  Room,
+  TypedEventEmitter,
 } from "matrix-js-sdk/src/matrix";
 import {
   CallMembership,
   Focus,
+  MatrixRTCSessionEvent,
+  MatrixRTCSessionEventHandlerMap,
   SessionMembershipData,
 } from "matrix-js-sdk/src/matrixrtc";
 import {
@@ -229,3 +233,30 @@ export async function withRemoteMedia(
     vm.destroy();
   }
 }
+
+export class MockRTCSession extends TypedEventEmitter<
+  MatrixRTCSessionEvent,
+  MatrixRTCSessionEventHandlerMap
+> {
+  public constructor(
+    public readonly room: Room,
+    private localMembership: CallMembership,
+    public memberships: CallMembership[] = [],
+  ) {
+    super();
+  }
+
+  public withMemberships(
+    rtcMembers: Observable<Partial<CallMembership>[]>,
+  ): MockRTCSession {
+    rtcMembers.subscribe((m) => {
+      const old = this.memberships;
+      // always prepend the local participant
+      const updated = [this.localMembership, ...(m as CallMembership[])];
+      this.memberships = updated;
+      this.emit(MatrixRTCSessionEvent.MembershipsChanged, old, updated);
+    });
+
+    return this;
+  }
+}