when the hint fn returns error, the scheduling queue logs the error and treats it as QueueAfterBackoff.

Co-authored-by: Kensei Nakada <handbomusic@gmail.com>

Co-authored-by: Kante Yin <kerthcet@gmail.com>

Co-authored-by: XsWack <xushiwei5@huawei.com>

pkg/scheduler/util/utils_test.go

@@ -31,6 +31,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/net"
 	clientsetfake "k8s.io/client-go/kubernetes/fake"
 	clienttesting "k8s.io/client-go/testing"
+	"k8s.io/klog/v2"
 	extenderv1 "k8s.io/kube-scheduler/extender/v1"
 )
 
@@ -487,3 +488,57 @@ func Test_As_Node(t *testing.T) {
 		})
 	}
 }
+
+// Test_As_KMetadata tests the As function with Pod.
+func Test_As_KMetadata(t *testing.T) {
+	tests := []struct {
+		name    string
+		oldObj  interface{}
+		newObj  interface{}
+		wantErr bool
+	}{
+		{
+			name:    "nil old Pod",
+			oldObj:  nil,
+			newObj:  &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "foo"}},
+			wantErr: false,
+		},
+		{
+			name:    "nil new Pod",
+			oldObj:  &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "foo"}},
+			newObj:  nil,
+			wantErr: false,
+		},
+		{
+			name:    "two different kinds of objects",
+			oldObj:  &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "foo"}},
+			newObj:  &v1.Node{ObjectMeta: metav1.ObjectMeta{Name: "foo"}},
+			wantErr: false,
+		},
+		{
+			name:    "unknown old type",
+			oldObj:  "unknown type",
+			wantErr: true,
+		},
+		{
+			name:    "unknown new type",
+			newObj:  "unknown type",
+			wantErr: true,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			_, _, err := As[klog.KMetadata](tc.oldObj, tc.newObj)
+			if err != nil && !tc.wantErr {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if tc.wantErr {
+				if err == nil {
+					t.Fatalf("expected error, but got nil")
+				}
+				return
+			}
+		})
+	}
+}