diff --git a/cmd/kubeadm/app/cmd/BUILD b/cmd/kubeadm/app/cmd/BUILD
index 5624cc9705e..085216bd9a5 100644
--- a/cmd/kubeadm/app/cmd/BUILD
+++ b/cmd/kubeadm/app/cmd/BUILD
@@ -82,6 +82,7 @@ go_library(
 go_test(
     name = "go_default_test",
     srcs = [
+        "completion_test.go",
         "join_test.go",
         "reset_test.go",
         "token_test.go",
@@ -96,6 +97,7 @@ go_test(
         "//cmd/kubeadm/app/preflight:go_default_library",
         "//pkg/api/legacyscheme:go_default_library",
         "//vendor/github.com/ghodss/yaml:go_default_library",
+        "//vendor/github.com/spf13/cobra:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/api/errors:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
diff --git a/cmd/kubeadm/app/cmd/completion.go b/cmd/kubeadm/app/cmd/completion.go
index 48282b20dd2..33d5526f9a8 100644
--- a/cmd/kubeadm/app/cmd/completion.go
+++ b/cmd/kubeadm/app/cmd/completion.go
@@ -89,13 +89,17 @@ var (
 	}
 )
 
-// NewCmdCompletion return command for executing "kubeadm completion" command
-func NewCmdCompletion(out io.Writer, boilerPlate string) *cobra.Command {
+// GetSupportedShells returns a list of supported shells
+func GetSupportedShells() []string {
 	shells := []string{}
 	for s := range completionShells {
 		shells = append(shells, s)
 	}
+	return shells
+}
 
+// NewCmdCompletion returns the "kubeadm completion" command
+func NewCmdCompletion(out io.Writer, boilerPlate string) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:     "completion SHELL",
 		Short:   i18n.T("Output shell completion code for the specified shell (bash or zsh)."),
@@ -105,7 +109,7 @@ func NewCmdCompletion(out io.Writer, boilerPlate string) *cobra.Command {
 			err := RunCompletion(out, boilerPlate, cmd, args)
 			kubeadmutil.CheckErr(err)
 		},
-		ValidArgs: shells,
+		ValidArgs: GetSupportedShells(),
 	}
 
 	return cmd
diff --git a/cmd/kubeadm/app/cmd/completion_test.go b/cmd/kubeadm/app/cmd/completion_test.go
new file mode 100644
index 00000000000..e13eed481fd
--- /dev/null
+++ b/cmd/kubeadm/app/cmd/completion_test.go
@@ -0,0 +1,95 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cmd
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/spf13/cobra"
+)
+
+const shellsError = "Unexpected empty completion shells list"
+
+func TestNewCmdCompletion(t *testing.T) {
+	var out bytes.Buffer
+	shells := GetSupportedShells()
+	if len(shells) == 0 {
+		t.Errorf(shellsError)
+	}
+	// test NewCmdCompletion with a valid shell.
+	// use a dummy parent command as NewCmdCompletion needs it.
+	parentCmd := &cobra.Command{}
+	args := []string{"completion", shells[0]}
+	parentCmd.SetArgs(args)
+	cmd := NewCmdCompletion(&out, "")
+	parentCmd.AddCommand(cmd)
+	if err := parentCmd.Execute(); err != nil {
+		t.Errorf("Cannot exectute NewCmdCompletion: %v", err)
+	}
+}
+
+func TestRunCompletion(t *testing.T) {
+	var out bytes.Buffer
+	type TestCase struct {
+		name          string
+		args          []string
+		expectedError bool
+	}
+
+	testCases := []TestCase{
+		{
+			name:          "invalid: missing argument",
+			args:          []string{},
+			expectedError: true,
+		},
+		{
+			name:          "invalid: too many arguments",
+			args:          []string{"", ""},
+			expectedError: true,
+		},
+		{
+			name:          "invalid: unsupported shell name",
+			args:          []string{"unsupported"},
+			expectedError: true,
+		},
+	}
+
+	// test all supported shells
+	shells := GetSupportedShells()
+	if len(shells) == 0 {
+		t.Errorf(shellsError)
+	}
+	for _, shell := range shells {
+		test := TestCase{
+			name: "valid: test shell " + shell,
+			args: []string{shell},
+		}
+		testCases = append(testCases, test)
+	}
+
+	// use dummy cobra commands
+	parentCmd := &cobra.Command{}
+	cmd := &cobra.Command{}
+	parentCmd.AddCommand(cmd)
+
+	for _, tc := range testCases {
+		if err := RunCompletion(&out, "", cmd, tc.args); (err != nil) != tc.expectedError {
+			t.Errorf("Test case %q: TestRunCompletion expected error: %v, saw: %v", tc.name, tc.expectedError, (err != nil))
+		}
+	}
+}