Add stub heartbeat method to test subscription writers

Author: endigma

v2/pkg/engine/resolve/event_loop_test.go

@@ -51,6 +51,10 @@ func (f *FakeSubscriptionWriter) Complete() {
 	f.messageCountOnComplete = len(f.writtenMessages)
 }
 
+func (f *FakeSubscriptionWriter) Heartbeat() error {
+	return nil
+}
+
 func (f *FakeSubscriptionWriter) Close(SubscriptionCloseKind) {
 	f.mu.Lock()
 	defer f.mu.Unlock()

v2/pkg/engine/resolve/resolve_test.go

@@ -4777,6 +4777,10 @@ func (s *SubscriptionRecorder) Complete() {
 	s.complete.Store(true)
 }
 
+func (s *SubscriptionRecorder) Heartbeat() error {
+	return nil
+}
+
 func (s *SubscriptionRecorder) Close(_ SubscriptionCloseKind) {
 	s.closed.Store(true)
 }