var logFiltered string
	if !req.Delta.IsEmpty() && !requiresResourceNamesModification(w.TypeUrl) {
		// Some types opt out of this and natively handle req.Delta
		logFiltered = " filtered:" + strconv.Itoa(len(w.ResourceNames)-len(req.Delta.Subscribed))
		w = &model.WatchedResource{
			TypeUrl:       w.TypeUrl,
			ResourceNames: req.Delta.Subscribed.UnsortedList(),
		}
	}

	var res model.Resources

		if dir == model.TrafficDirectionInbound {
			// Append all inbound clusters because in both stow/delta we always build all inbound clusters.
			// In reality, the delta building is only for outbound clusters. We need to revist here once we support delta for inbound.
			// So deletedClusters.Difference(builtClusters) would give us the correct deleted inbound clusters.
			deletedClusters.Insert(cluster)

	"istio.io/istio/pkg/util/sets"
)

var knownOptimizationGaps = sets.New(
	"BlackHoleCluster",
	"InboundPassthroughCluster",
	"PassthroughCluster",
)

// compareDiff compares a Delta and SotW XDS response. This allows checking that the Delta XDS
// response returned the optimal result. Checks include correctness checks (e.g. if a config changed,
// we must include it) and possible optimizations (e.g. we sent a config, but it was not changed).

  EXPECT_TRUE(result.ok());
  EXPECT_EQ(compilation_status.Delta(kMlirCombinedMlirSuccess), 1);
  EXPECT_EQ(compilation_status.Delta(kMlirCombinedMlirFailure), 0);
  EXPECT_EQ(compilation_status.Delta(kMlirCombinedOldSuccess), 1);
  EXPECT_EQ(compilation_status.Delta(kMlirCombinedOldFailure), 0);
  // Old bridge should never be called at all.
  EXPECT_EQ(compilation_status.Delta(kOldBridgeMlirFilteredFailure), 0);

	).Get()

	// EnableUnsafeDeltaTest enables runtime checks to test Delta XDS efficiency. This should never be enabled in
	// production.
	EnableUnsafeDeltaTest = env.Register(
		"UNSAFE_PILOT_ENABLE_DELTA_TEST",
		false,
		"If enabled, addition runtime tests for Delta XDS efficiency are added. "+
			"These checks are extremely expensive, so this should be used only for testing, not production.",

				proxy.PrevSidecarScope.SetDestinationRulesForTesting(tc.prevConfigs)
			}
			clusters, removed, delta := cg.DeltaClusters(proxy, tc.configUpdated,
				&model.WatchedResource{ResourceNames: tc.watchedResourceNames})
			if delta != tc.usedDelta {
				t.Errorf("un expected delta, want %v got %v", tc.usedDelta, delta)
			}
			assert.Equal(t, removed, tc.removedClusters)

	// housekeeping routine. This test registers the pod, removes the unwanted pod, then calls into
	// HandlePodCleanups a few more times. We should only see one Destroy() event. podKiller runs
	// within a goroutine so a two second delay should be enough time to
	// mark the pod as killed (within this test case).

	kubelet.HandlePodCleanups(ctx)

	// assert that unwanted pods were killed