1. Install the github.com/gorilla/websocket and github.com/stretchr/testify/assert packages using the go get command, as follows:

$ go get github.com/gorilla/websocket
$ go get github.com/stretchr/testify/assert

2. Create websocket-server_test.go where we will create a test server, connect to it using the Gorilla client, and eventually read and write messages to test the connection, as follows:

package main
import 
(
  "net/http"
  "net/http/httptest"
  "strings"
  "testing"
  "github.com/gorilla/websocket"
  "github.com/stretchr/testify/assert"
)
func TestWebSocketServer(t *testing.T) 
{
  server := httptest.NewServer(http.HandlerFunc
  (HandleClients))
  defer server.Close()
  u := "ws" + strings.TrimPrefix(server.URL, "http")
  socket, _, err := websocket.DefaultDialer.Dial(u, nil)
  if err != nil 
  {
    t.Fatalf("%v", err)
  }
  defer socket.Close()
  m := Message{Message: "hello"}
  if err := socket.WriteJSON(&m); err != nil 
  {
    t.Fatalf("%v", err)
  }
  var message Message
  err = socket.ReadJSON(&message)
  if err != nil 
  {
    t.Fatalf("%v", err)
  }
  assert.Equal(t, "hello", message.Message, "they 
  should be equal")
}