added NICK no NICK given test + implementation with new errorcode

src/server.js

@@ -7,6 +7,7 @@ const ERR_NOSUCHCHANNEL = '403'
 const ERR_CANNOTSENDTOCHAN = '404'
 const ERR_UNKNOWNCOMMAND = '421'
 const ERR_ERRONEUSNICKNAME = '432'
+const ERR_NONICKNAMEGIVEN = '431'
 const ERR_NICKNAMEINUSE = '433'
 const ERR_NEEDMOREPARAMS = '461'
 
@@ -39,7 +40,7 @@ server.create = function create() {
 
 
                     } else {
-                        socket.write("ERROR: NO NICKNAME PROVIDED")
+                        socket.write(ERR_NONICKNAMEGIVEN, "ERROR: NO NICKNAME PROVIDED")
                     }
 
                     break;

test/server.js

@@ -40,7 +40,7 @@ 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()
@@ -57,4 +57,20 @@ describe('IRC server', function () {
                 mockedSock.emit('data', Buffer.from("NICK some_nick\r\n", "ascii"))
             })
         })
+    describe("NICK no NICK given", function () {
+        it("should handle a NICK command -> NICK ", function (done) {
+            const server = IRCServer.create()
+            let mockedSock = new EventEmitter()
+            mockedSock.write = function (data) {
+                assert.equal(data.toString("ascii"), "431")
+                done()
+            }
+            mockedSock.destroy = function () {
+                done("Destroyed socket without answering")
+            }
+
+            server.emit("connection", mockedSock)
+            mockedSock.emit('data', Buffer.from("NICK \r\n", "ascii"))
+        })
+    })
 })