add a comment on heartbeater test logic

internal/auto_heartbeater_test.go

@@ -45,6 +45,9 @@ func TestAutoHearbeater_Run(t *testing.T) {
 		}
 	)
 
+	// Run is a sync function that is spawned in a goroutine normally.
+	// So instead of asserting the results we can verify that the function exists.
+
 	t.Run("worker stop channel", func(t *testing.T) {
 		stopCh := make(chan struct{})
 		invoker := &MockServiceInvoker{}
@@ -53,7 +56,7 @@ func TestAutoHearbeater_Run(t *testing.T) {
 		hearbeater := newHeartbeater(stopCh, invoker, logger, clock, activityType, workflowExecution)
 
 		close(stopCh)
-
+		
 		hearbeater.Run(context.Background(), time.Second)
 	})
 	t.Run("context done", func(t *testing.T) {