Add hello world http methode and test

server/plugin.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"fmt"
+	"net/http"
 	"sync"
 
 	"github.com/mattermost/mattermost-server/plugin"
@@ -17,4 +19,8 @@ type Plugin struct {
 	configuration *configuration
 }
 
+func (p *Plugin) ServeHTTP(c *plugin.Context, w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "Hello, world!")
+}
+
 // See https://developers.mattermost.com/extend/plugins/server/reference/

server/plugin_test.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"io/ioutil"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestServeHTTP(t *testing.T) {
+	assert := assert.New(t)
+	plugin := Plugin{}
+	w := httptest.NewRecorder()
+	r := httptest.NewRequest("GET", "/", nil)
+
+	plugin.ServeHTTP(nil, w, r)
+
+	result := w.Result()
+	assert.NotNil(result)
+	bodyBytes, err := ioutil.ReadAll(result.Body)
+	assert.Nil(err)
+	bodyString := string(bodyBytes)
+
+	assert.Equal("Hello, world!", bodyString)
+}