kubelet/userns: Add unit test

Signed-off-by: Rodrigo Campos <rodrigoca@microsoft.com>

pkg/kubelet/userns/userns_manager_test.go

@@ -47,6 +47,8 @@ type testUserNsPodsManager struct {
 	podList        []types.UID
 	userns         bool
 	maxPods        int
+	mappingFirstID uint32
+	mappingLen     uint32
 }
 
 func (m *testUserNsPodsManager) GetPodDir(podUID types.UID) string {
@@ -71,6 +73,9 @@ func (m *testUserNsPodsManager) HandlerSupportsUserNamespaces(runtimeHandler str
 }
 
 func (m *testUserNsPodsManager) GetKubeletMappings() (uint32, uint32, error) {
+	if m.mappingFirstID != 0 {
+		return m.mappingFirstID, m.mappingLen, nil
+	}
 	return minimumMappingUID, mappingLen, nil
 }
 
@@ -133,6 +138,60 @@ func TestUserNsManagerAllocate(t *testing.T) {
 	}
 }
 
+func TestMakeUserNsManager(t *testing.T) {
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, pkgfeatures.UserNamespacesSupport, true)()
+
+	cases := []struct {
+		name           string
+		mappingFirstID uint32
+		mappingLen     uint32
+		maxPods        int
+		success        bool
+	}{
+		{
+			name:    "default",
+			success: true,
+		},
+		{
+			name:           "firstID not multiple",
+			mappingFirstID: 65536 + 1,
+		},
+		{
+			name:           "firstID is less than 65535",
+			mappingFirstID: 1,
+		},
+		{
+			name:           "mappingLen not multiple",
+			mappingFirstID: 65536,
+			mappingLen:     65536 + 1,
+		},
+		{
+			name:           "range can't fit maxPods",
+			mappingFirstID: 65536,
+			mappingLen:     65536,
+			maxPods:        2,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			testUserNsPodsManager := &testUserNsPodsManager{
+				podDir:         t.TempDir(),
+				mappingFirstID: tc.mappingFirstID,
+				mappingLen:     tc.mappingLen,
+				maxPods:        tc.maxPods,
+			}
+			_, err := MakeUserNsManager(testUserNsPodsManager)
+
+			if tc.success {
+				assert.NoError(t, err)
+			} else {
+				assert.Error(t, err)
+			}
+		})
+	}
+}
+
 func TestUserNsManagerParseUserNsFile(t *testing.T) {
 	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, pkgfeatures.UserNamespacesSupport, true)()
 
@@ -404,3 +463,25 @@ func TestMakeUserNsManagerFailsListPod(t *testing.T) {
 	assert.Error(t, err)
 	assert.ErrorContains(t, err, "read pods from disk")
 }
+
+func TestRecordBounds(t *testing.T) {
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, pkgfeatures.UserNamespacesSupport, true)()
+
+	// Allow exactly for 1 pod
+	testUserNsPodsManager := &testUserNsPodsManager{
+		mappingFirstID: 65536,
+		mappingLen:     65536,
+		maxPods:        1,
+	}
+	m, err := MakeUserNsManager(testUserNsPodsManager)
+	require.NoError(t, err)
+
+	// The first pod allocation should succeed.
+	err = m.record(types.UID(fmt.Sprintf("%d", 0)), 65536, 65536)
+	require.NoError(t, err)
+
+	// The next allocation should fail, as there is no space left.
+	err = m.record(types.UID(fmt.Sprintf("%d", 2)), uint32(2*65536), 65536)
+	assert.Error(t, err)
+	assert.ErrorContains(t, err, "out of range")
+}