Fix deployment unit test by adding a dummy update reactor

federation/pkg/federation-controller/deployment/deploymentcontroller.go

@@ -420,8 +420,10 @@ func (fdc *DeploymentController) schedule(fd *extensionsv1.Deployment, clusters
 	if fdPref != nil { // create a new planner if user specified a preference
 		plannerToBeUsed = planner.NewPlanner(fdPref)
 	}
-
-	replicas := int64(*fd.Spec.Replicas)
+	replicas := int64(0)
+	if fd.Spec.Replicas != nil {
+		replicas = int64(*fd.Spec.Replicas)
+	}
 	var clusterNames []string
 	for _, cluster := range clusters {
 		clusterNames = append(clusterNames, cluster.Name)

federation/pkg/federation-controller/deployment/deploymentcontroller_test.go

@@ -85,6 +85,9 @@ func TestDeploymentController(t *testing.T) {
 	cluster2 := NewCluster("cluster2", apiv1.ConditionTrue)
 
 	fakeClient := &fakefedclientset.Clientset{}
+	// Add an update reactor on fake client to return the desired updated object.
+	// This is a hack to workaround https://github.com/kubernetes/kubernetes/issues/40939.
+	AddFakeUpdateReactor("deployments", &fakeClient.Fake)
 	RegisterFakeList("clusters", &fakeClient.Fake, &fedv1.ClusterList{Items: []fedv1.Cluster{*cluster1}})
 	deploymentsWatch := RegisterFakeWatch("deployments", &fakeClient.Fake)
 	clusterWatch := RegisterFakeWatch("clusters", &fakeClient.Fake)

federation/pkg/federation-controller/util/test/test_helper.go

@@ -226,6 +226,18 @@ func RegisterFakeCopyOnUpdate(resource string, client *core.Fake, watcher *Watch
 	return objChan
 }
 
+// Adds an update reactor to the given fake client.
+// The reactor just returns the object passed to update action.
+// This is used as a hack to workaround https://github.com/kubernetes/kubernetes/issues/40939.
+// Without this, all update actions using fake client return empty objects.
+func AddFakeUpdateReactor(resource string, client *core.Fake) {
+	client.AddReactor("update", resource, func(action core.Action) (bool, runtime.Object, error) {
+		updateAction := action.(core.UpdateAction)
+		originalObj := updateAction.GetObject()
+		return true, originalObj, nil
+	})
+}
+
 // GetObjectFromChan tries to get an api object from the given channel
 // within a reasonable time.
 func GetObjectFromChan(c chan runtime.Object) runtime.Object {