Merge pull request #46759 from zjj2wry/kubelet

Automatic merge from submit-queue (batch tested with PRs 46734, 46810, 46759, 46259, 46771)

Improve code coverage for pkg/kubelet/images/image_gc_manager

**What this PR does / why we need it**:
#39559 #40780

code coverage from 74.5% to 77.4%

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

pkg/kubelet/images/image_gc_manager_test.go

@@ -463,3 +463,63 @@ func TestGarbageCollectImageNotOldEnough(t *testing.T) {
 	assert.EqualValues(1024, spaceFreed)
 	assert.Len(fakeRuntime.ImageList, 1)
 }
+
+func TestValidateImageGCPolicy(t *testing.T) {
+	testCases := []struct {
+		name          string
+		imageGCPolicy ImageGCPolicy
+		expectErr     string
+	}{
+		{
+			name: "Test for LowThresholdPercent < HighThresholdPercent",
+			imageGCPolicy: ImageGCPolicy{
+				HighThresholdPercent: 2,
+				LowThresholdPercent:  1,
+			},
+		},
+		{
+			name: "Test for HighThresholdPercent < 0,",
+			imageGCPolicy: ImageGCPolicy{
+				HighThresholdPercent: -1,
+			},
+			expectErr: "invalid HighThresholdPercent -1, must be in range [0-100]",
+		},
+		{
+			name: "Test for HighThresholdPercent > 100",
+			imageGCPolicy: ImageGCPolicy{
+				HighThresholdPercent: 101,
+			},
+			expectErr: "invalid HighThresholdPercent 101, must be in range [0-100]",
+		},
+		{
+			name: "Test for LowThresholdPercent < 0",
+			imageGCPolicy: ImageGCPolicy{
+				LowThresholdPercent: -1,
+			},
+			expectErr: "invalid LowThresholdPercent -1, must be in range [0-100]",
+		},
+		{
+			name: "Test for LowThresholdPercent > 100",
+			imageGCPolicy: ImageGCPolicy{
+				LowThresholdPercent: 101,
+			},
+			expectErr: "invalid LowThresholdPercent 101, must be in range [0-100]",
+		},
+		{
+			name: "Test for LowThresholdPercent > HighThresholdPercent",
+			imageGCPolicy: ImageGCPolicy{
+				HighThresholdPercent: 1,
+				LowThresholdPercent:  2,
+			},
+			expectErr: "LowThresholdPercent 2 can not be higher than HighThresholdPercent 1",
+		},
+	}
+
+	for _, tc := range testCases {
+		if _, err := NewImageGCManager(nil, nil, nil, nil, tc.imageGCPolicy); err != nil {
+			if err.Error() != tc.expectErr {
+				t.Errorf("[%s:]Expected err:%v, but got:%v", tc.name, tc.expectErr, err.Error())
+			}
+		}
+	}
+}