test(multiplayer): verify two-player proposal round trip

server/matcher/worker.go

@@ -47,6 +47,7 @@ type Worker struct {
 	Now      func() time.Time
 	NextID   func() string
 	Prepare  PrepareFunc
+	OnError  func(error)
 }
 
 // Run polls until cancellation. A failed attempt is returned so a supervisor
@@ -57,6 +58,9 @@ func (w Worker) Run(ctx context.Context, interval time.Duration) error {
 	}
 	for {
 		if _, err := w.RunOnce(ctx); err != nil {
+			if w.OnError != nil {
+				w.OnError(err)
+			}
 			if errors.Is(err, ErrWorkerNotConfigured) || errors.Is(err, ErrUnsupportedPlaylist) || errors.Is(err, ErrInvalidMatcherSize) {
 				return err
 			}