fix flake in dra test 'TestPlugin'

TestPlugin/multi-claims-binding-conditions-all-success/PreEnqueue
flakes due to the assumed cache not been synced with the initial
store. The test waits until the registered handler used by the
assumed cache has synced before proceeding with the test

Author: tkashem

pkg/scheduler/framework/plugins/dynamicresources/dynamicresources_test.go

@@ -41,6 +41,7 @@ import (
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes/fake"
 	cgotesting "k8s.io/client-go/testing"
+	"k8s.io/client-go/tools/cache"
 	"k8s.io/client-go/tools/events"
 	resourceslicetracker "k8s.io/dynamic-resource-allocation/resourceslice/tracker"
 	kubeschedulerconfigv1 "k8s.io/kube-scheduler/config/v1"
@@ -2062,7 +2063,21 @@ func setup(t *testing.T, args *config.DynamicResourcesArgs, nodes []*v1.Node, cl
 	}
 	resourceSliceTracker, err := resourceslicetracker.StartTracker(tCtx, resourceSliceTrackerOpts)
 	require.NoError(t, err, "couldn't start resource slice tracker")
-	tc.draManager = NewDRAManager(tCtx, assumecache.NewAssumeCache(tCtx.Logger(), tc.informerFactory.Resource().V1().ResourceClaims().Informer(), "resource claim", "", nil), resourceSliceTracker, tc.informerFactory)
+
+	claimsCache := assumecache.NewAssumeCache(tCtx.Logger(), tc.informerFactory.Resource().V1().ResourceClaims().Informer(), "resource claim", "", nil)
+	// NewAssumeCache calls the informer's AddEventHandler method to register
+	// a handler in order to stay in sync with the informer's store, but
+	// NewAssumeCache does not return the ResourceEventHandlerRegistration.
+	// We call AddEventHandler of the assume cache, passing it a noop
+	// ResourceEventHandler in order to get access to the
+	// ResourceEventHandlerRegistration returned by the informer.
+	//
+	// This is not the registered handler that is used by the DRA
+	// manager, but it is close enough because the assume cache
+	// uses a single boolean for "is synced" for all handlers.
+	registeredHandler := claimsCache.AddEventHandler(cache.ResourceEventHandlerFuncs{})
+
+	tc.draManager = NewDRAManager(tCtx, claimsCache, resourceSliceTracker, tc.informerFactory)
 	opts := []runtime.Option{
 		runtime.WithClientSet(tc.client),
 		runtime.WithInformerFactory(tc.informerFactory),
@@ -2103,6 +2118,11 @@ func setup(t *testing.T, args *config.DynamicResourcesArgs, nodes []*v1.Node, cl
 	})
 
 	tc.informerFactory.WaitForCacheSync(tc.ctx.Done())
+	// The above does not tell us if the registered handler (from NewAssumeCache)
+	// is synced, we need to wait until HasSynced of the handler returns
+	// true, this ensures that the assume cache is in sync with the informer's
+	// store which has been informed by at least one full LIST of the underlying storage.
+	cache.WaitForCacheSync(tc.ctx.Done(), registeredHandler.HasSynced)
 
 	for _, node := range nodes {
 		nodeInfo := framework.NewNodeInfo()