Fix kubeadm unit tests relying on internet access

cmd/kubeadm/app/cmd/config.go

@@ -358,7 +358,7 @@ func NewCmdConfigImages(out io.Writer) *cobra.Command {
 		Short: "Interact with container images used by kubeadm.",
 		RunE:  cmdutil.SubCmdRunE("images"),
 	}
-	cmd.AddCommand(NewCmdConfigImagesList(out))
+	cmd.AddCommand(NewCmdConfigImagesList(out, nil))
 	cmd.AddCommand(NewCmdConfigImagesPull())
 	return cmd
 }
@@ -416,12 +416,18 @@ func (ip *ImagesPull) PullAll() error {
 }
 
 // NewCmdConfigImagesList returns the "kubeadm config images list" command
-func NewCmdConfigImagesList(out io.Writer) *cobra.Command {
+func NewCmdConfigImagesList(out io.Writer, mockK8sVersion *string) *cobra.Command {
 	cfg := &kubeadmapiv1alpha2.MasterConfiguration{}
 	kubeadmscheme.Scheme.Default(cfg)
 	var cfgPath, featureGatesString string
 	var err error
 
+	// This just sets the kubernetes version for unit testing so kubeadm won't try to
+	// lookup the latest release from the internet.
+	if mockK8sVersion != nil {
+		cfg.KubernetesVersion = *mockK8sVersion
+	}
+
 	cmd := &cobra.Command{
 		Use:   "list",
 		Short: "Print a list of images kubeadm will use. The configuration file is used in case any images or image repositories are customized.",

cmd/kubeadm/app/cmd/config_test.go

@@ -34,11 +34,15 @@ import (
 
 const (
 	defaultNumberOfImages = 8
+	// dummyKubernetesVersion is just used for unit testing, in order to not make
+	// kubeadm lookup dl.k8s.io to resolve what the latest stable release is
+	dummyKubernetesVersion = "v1.10.0"
 )
 
 func TestNewCmdConfigImagesList(t *testing.T) {
 	var output bytes.Buffer
-	images := cmd.NewCmdConfigImagesList(&output)
+	mockK8sVersion := dummyKubernetesVersion
+	images := cmd.NewCmdConfigImagesList(&output, &mockK8sVersion)
 	images.Run(nil, nil)
 	actual := strings.Split(output.String(), "\n")
 	if len(actual) != defaultNumberOfImages {
@@ -63,7 +67,7 @@ func TestImagesListRunWithCustomConfigPath(t *testing.T) {
 			configContents: []byte(dedent.Dedent(`
 				apiVersion: kubeadm.k8s.io/v1alpha2
 				kind: MasterConfiguration
-				kubernetesVersion: 1.10.1
+				kubernetesVersion: v1.10.1
 			`)),
 		},
 		{
@@ -75,9 +79,9 @@ func TestImagesListRunWithCustomConfigPath(t *testing.T) {
 			configContents: []byte(dedent.Dedent(`
 				apiVersion: kubeadm.k8s.io/v1alpha2
 				kind: MasterConfiguration
-				kubernetesVersion: 1.11.0
+				kubernetesVersion: v1.11.0
 				featureGates:
-				    CoreDNS: True
+				  CoreDNS: True
 			`)),
 		},
 	}
@@ -96,7 +100,9 @@ func TestImagesListRunWithCustomConfigPath(t *testing.T) {
 				t.Fatalf("Failed writing a config file: %v", err)
 			}
 
-			i, err := cmd.NewImagesList(configFilePath, &kubeadmapiv1alpha2.MasterConfiguration{})
+			i, err := cmd.NewImagesList(configFilePath, &kubeadmapiv1alpha2.MasterConfiguration{
+				KubernetesVersion: dummyKubernetesVersion,
+			})
 			if err != nil {
 				t.Fatalf("Failed getting the kubeadm images command: %v", err)
 			}
@@ -127,6 +133,9 @@ func TestConfigImagesListRunWithoutPath(t *testing.T) {
 		{
 			name:           "empty config",
 			expectedImages: defaultNumberOfImages,
+			cfg: kubeadmapiv1alpha2.MasterConfiguration{
+				KubernetesVersion: dummyKubernetesVersion,
+			},
 		},
 		{
 			name: "external etcd configuration",
@@ -136,6 +145,7 @@ func TestConfigImagesListRunWithoutPath(t *testing.T) {
 						Endpoints: []string{"https://some.etcd.com:2379"},
 					},
 				},
+				KubernetesVersion: dummyKubernetesVersion,
 			},
 			expectedImages: defaultNumberOfImages - 1,
 		},
@@ -145,6 +155,7 @@ func TestConfigImagesListRunWithoutPath(t *testing.T) {
 				FeatureGates: map[string]bool{
 					features.CoreDNS: true,
 				},
+				KubernetesVersion: dummyKubernetesVersion,
 			},
 			expectedImages: defaultNumberOfImages,
 		},
@@ -198,6 +209,7 @@ func TestMigrate(t *testing.T) {
 	cfg := []byte(dedent.Dedent(`
 		apiVersion: kubeadm.k8s.io/v1alpha2
 		kind: MasterConfiguration
+		kubernetesVersion: v1.10.0
 	`))
 	configFile, cleanup := tempConfig(t, cfg)
 	defer cleanup()

cmd/kubeadm/test/util.go

@@ -61,6 +61,7 @@ func SetupMasterConfigurationFile(t *testing.T, tmpdir string, cfg *kubeadmapi.M
 		  bindPort: {{.API.BindPort}}
 		nodeRegistration:
 		  name: {{.NodeRegistration.Name}}
+		kubernetesVersion: v1.10.0
 		`)))
 
 	f, err := os.Create(cfgPath)