Address review feedback

Author: robintown

src/state/MediaViewModel.test.ts

@@ -182,8 +182,9 @@ test("switch cameras", async () => {
     async (vm) => {
       // Switch to back camera
       getValue(vm.switchCamera$)!();
-      expect(restartTrack).toHaveBeenCalledTimes(1);
-      expect(restartTrack).toHaveBeenCalledWith({ facingMode: "environment" });
+      expect(restartTrack).toHaveBeenCalledExactlyOnceWith({
+        facingMode: "environment",
+      });
       await waitFor(() => {
         expect(selectVideoInput).toHaveBeenCalledTimes(1);
         expect(selectVideoInput).toHaveBeenCalledWith("back camera");

src/state/MediaViewModel.ts

@@ -456,11 +456,13 @@ export class LocalUserMediaViewModel extends BaseUserMediaViewModel {
         const track = v?.publication?.track;
         if (!(track instanceof LocalVideoTrack)) return of(null);
         return merge(
-          // Watch for track restarts because they indicate a camera switch
+          // Watch for track restarts because they indicate a camera switch.
+          // This event is also emitted when unmuting the track object.
           fromEvent(track, TrackEvent.Restarted).pipe(
             startWith(null),
             map(() => track),
           ),
+          // When the track object is muted, reset it to null.
           fromEvent(track, TrackEvent.Muted).pipe(map(() => null)),
         );
       }),