diff --git a/test/server.js b/test/server.js
index cd894f8..f1d244a 100644
--- a/test/server.js
+++ b/test/server.js
@@ -2,29 +2,29 @@ const assert = require('assert');
 const EventEmitter = require('events');
 const IRCServer = require("../src/server.js");
 
-describe('IRC server', function() {
-  describe('#create()', function() {
-    it("should return a socket server", function() {
-      const server = IRCServer.create()
-      assert.equal(server.eventNames().toString(), ["connection", "error"].toString())
+describe('IRC server', function () {
+    describe('#create()', function () {
+        it("should return a socket server", function () {
+            const server = IRCServer.create()
+            assert.equal(server.eventNames().toString(), ["connection", "error"].toString())
+        })
     })
-  })
-  describe("on('connection')", function() {
-    it("should handle a PING command -> PING irc.example.com", function(done) {
-      const server = IRCServer.create()
-      let mockedSock = new EventEmitter()
-      mockedSock.write = function(data) {
-        assert.equal(data.toString("ascii"), "PONG irc.example.com\r\n")
-        done()
-      }
-      mockedSock.destroy = function() {
-        done("Destroyed socket without answering")
-      }
+    describe("on('connection')", function () {
+        it("should handle a PING command -> PING irc.example.com", function (done) {
+            const server = IRCServer.create()
+            let mockedSock = new EventEmitter()
+            mockedSock.write = function (data) {
+                assert.equal(data.toString("ascii"), "PONG irc.example.com\r\n")
+                done()
+            }
+            mockedSock.destroy = function () {
+                done("Destroyed socket without answering")
+            }
 
-      server.emit("connection", mockedSock)
-      mockedSock.emit('data', Buffer.from("PING irc.example.com\r\n", "ascii"))
+            server.emit("connection", mockedSock)
+            mockedSock.emit('data', Buffer.from("PING irc.example.com\r\n", "ascii"))
+        })
     })
-  })
     describe("NICK OK", function () {
         it("should handle a NICK command -> NICK some_nickname", function (done) {
             const server = IRCServer.create()
@@ -40,5 +40,21 @@ describe('IRC server', function() {
             server.emit("connection", mockedSock)
             mockedSock.emit('data', Buffer.from("NICK some_nick\r\n", "ascii"))
         })
-    })
+    }),
+        describe("NICK already registered", function () {
+            it("should handle a NICK command -> NICK some_nickname", function (done) {
+                const server = IRCServer.create()
+                let mockedSock = new EventEmitter()
+                mockedSock.write = function (data) {
+                    assert.equal(data.toString("ascii"), "433")
+                    done()
+                }
+                mockedSock.destroy = function () {
+                    done("Destroyed socket without answering")
+                }
+
+                server.emit("connection", mockedSock)
+                mockedSock.emit('data', Buffer.from("NICK some_nick\r\n", "ascii"))
+            })
+        })
 })