Merge pull request #43450 from zjj2wry/003

Automatic merge from submit-queue (batch tested with PRs 43450, 42999, 43968)

unit test for kubectl config set-context

**What this PR does / why we need it**:
unit test for create context

**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**:
think you 

**Release note**:

```release-note
NONE
```

pkg/kubectl/cmd/config/BUILD

@@ -49,6 +49,7 @@ go_test(
     srcs = [
         "config_test.go",
         "create_authinfo_test.go",
+        "create_context_test.go",
         "current_context_test.go",
         "delete_cluster_test.go",
         "delete_context_test.go",

pkg/kubectl/cmd/config/create_context_test.go

@@ -0,0 +1,118 @@
+/*
+Copyright 2017 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 config
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"k8s.io/client-go/tools/clientcmd"
+	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
+)
+
+type createContextTest struct {
+	description    string
+	config         clientcmdapi.Config //initiate kubectl config
+	args           []string            //kubectl set-context args
+	flags          []string            //kubectl set-context flags
+	expected       string              //expectd out
+	expectedConfig clientcmdapi.Config //expect kubectl config
+}
+
+func TestCreateContext(t *testing.T) {
+	conf := clientcmdapi.Config{}
+	test := createContextTest{
+		description: "Testing for create a new context",
+		config:      conf,
+		args:        []string{"shaker-context"},
+		flags: []string{
+			"--cluster=cluster_nickname",
+			"--user=user_nickname",
+			"--namespace=namespace",
+		},
+		expected: `Context "shaker-context" set.` + "\n",
+		expectedConfig: clientcmdapi.Config{
+			Contexts: map[string]*clientcmdapi.Context{
+				"shaker-context": {AuthInfo: "user_nickname", Cluster: "cluster_nickname", Namespace: "namespace"}},
+		},
+	}
+	test.run(t)
+}
+func TestModifyContext(t *testing.T) {
+	conf := clientcmdapi.Config{
+		Contexts: map[string]*clientcmdapi.Context{
+			"shaker-context": {AuthInfo: "blue-user", Cluster: "big-cluster", Namespace: "saw-ns"},
+			"not-this":       {AuthInfo: "blue-user", Cluster: "big-cluster", Namespace: "saw-ns"}}}
+	test := createContextTest{
+		description: "Testing for modify a already exist context",
+		config:      conf,
+		args:        []string{"shaker-context"},
+		flags: []string{
+			"--cluster=cluster_nickname",
+			"--user=user_nickname",
+			"--namespace=namespace",
+		},
+		expected: `Context "shaker-context" set.` + "\n",
+		expectedConfig: clientcmdapi.Config{
+			Contexts: map[string]*clientcmdapi.Context{
+				"shaker-context": {AuthInfo: "user_nickname", Cluster: "cluster_nickname", Namespace: "namespace"},
+				"not-this":       {AuthInfo: "blue-user", Cluster: "big-cluster", Namespace: "saw-ns"}}},
+	}
+	test.run(t)
+}
+
+func (test createContextTest) run(t *testing.T) {
+	fakeKubeFile, err := ioutil.TempFile(os.TempDir(), "")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	defer os.Remove(fakeKubeFile.Name())
+	err = clientcmd.WriteToFile(test.config, fakeKubeFile.Name())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	pathOptions := clientcmd.NewDefaultPathOptions()
+	pathOptions.GlobalFile = fakeKubeFile.Name()
+	pathOptions.EnvVar = ""
+	buf := bytes.NewBuffer([]byte{})
+	cmd := NewCmdConfigSetContext(buf, pathOptions)
+	cmd.SetArgs(test.args)
+	cmd.Flags().Parse(test.flags)
+	if err := cmd.Execute(); err != nil {
+		t.Fatalf("unexpected error executing command: %v,kubectl set-context args: %v,flags: %v", err, test.args, test.flags)
+	}
+	config, err := clientcmd.LoadFromFile(fakeKubeFile.Name())
+	if err != nil {
+		t.Fatalf("unexpected error loading kubeconfig file: %v", err)
+	}
+	if len(test.expected) != 0 {
+		if buf.String() != test.expected {
+			t.Errorf("Fail in %q:\n expected %v\n but got %v\n", test.description, test.expected, buf.String())
+		}
+	}
+	if test.expectedConfig.Contexts != nil {
+		expectContext := test.expectedConfig.Contexts[test.args[0]]
+		actualContext := config.Contexts[test.args[0]]
+		if expectContext.AuthInfo != actualContext.AuthInfo || expectContext.Cluster != actualContext.Cluster ||
+			expectContext.Namespace != actualContext.Namespace {
+			t.Errorf("Fail in %q:\n expected Context %v\n but found %v in kubeconfig\n", test.description, expectContext, actualContext)
+		}
+	}
+}