diff --git a/federation/pkg/federation-controller/util/federated_informer.go b/federation/pkg/federation-controller/util/federated_informer.go
index 6f192a6b555..0064c4fcebc 100644
--- a/federation/pkg/federation-controller/util/federated_informer.go
+++ b/federation/pkg/federation-controller/util/federated_informer.go
@@ -96,6 +96,13 @@ type FederatedInformer interface {
 	Stop()
 }
 
+// FederatedInformer with extra method for setting fake clients.
+type FederatedInformerForTestOnly interface {
+	FederatedInformer
+
+	SetClientFactory(func(*federation_api.Cluster) (federation_release_1_4.Interface, error))
+}
+
 // A function that should be used to create an informer on the target object. Store should use
 // framework.DeletionHandlingMetaNamespaceKeyFunc as a keying function.
 type TargetInformerFactory func(*federation_api.Cluster, federation_release_1_4.Interface) (cache.Store, framework.ControllerInterface)
@@ -261,6 +268,13 @@ func (f *federatedInformerImpl) Start() {
 	go f.clusterInformer.controller.Run(f.clusterInformer.stopChan)
 }
 
+func (f *federatedInformerImpl) SetClientFactory(clientFactory func(*federation_api.Cluster) (federation_release_1_4.Interface, error)) {
+	f.Lock()
+	defer f.Unlock()
+
+	f.clientFactory = clientFactory
+}
+
 // GetClientsetForCluster returns a clientset for the cluster, if present.
 func (f *federatedInformerImpl) GetClientsetForCluster(clusterName string) (federation_release_1_4.Interface, error) {
 	f.Lock()