Use

1. Instantiate a server to intercept socket.io connection:

var io = require("socket.io-client");
var fixtureSocket = require("can-fixture-socket");
var mockServer = new fixtureSocket.Server(io);

2. Mock socket.io server behaviour:

mockServer.on("connection", function(){
  mockServer.emit("notifications", [{text: "A new notification"}]);
});

mockServer.on("some event", function(data, ackCb){
  console.log("Client send some ", data);
  ackCb("thanks");
});

3. Test your client app:

var socket = io("http://localhost:8080/ws");
socket.emit("some event", "some data", function(data){
  assert.equal(data, "thanks", "Server acknowledged our event");
});

Examples

CRUD service with fixture store

Lets see how we can test a possible implementation of a CRUD service that utilizes socket.io ACK callbacks. We will use fixture store to emulate our CRUD storage and link it to our mocked server.

var fixture = require("can-fixture");

// First, lets create fixture store:
var fixtureStore = fixture.store([
  {id: 1, title: "One", rank: "good"},
  {id: 2, title: "Two", rank: "average"},
  {id: 3, title: "Three", rank: "good"}
], new canSet.Algebra({}));

// And instantiate a mocked server:
var io = require("socket.io-client");
var fixtureSocket = require("can-fixture-socket");
var mockServer = new fixtureSocket.Server(io);

Fixture store is designed to work with XHR requests, thus its methods take two arguments: request and response. See [can-fixture.Store.prototype.getListData] for more details. Our mocked server can listen to socket events and its event listener expects data and an optional ACK callback. To convert a request handler to an event listener we can use requestHandlerToListener:

Now we can create socket event listeners for our CRUD operations:

var toListener = fixtureSocket.requestHandlerToListener
mockServer.on("messages find",   toListener( fixtureStore.getListData ));
mockServer.on("messages get",    toListener( fixtureStore.getData     ));
mockServer.on("messages remove", toListener( fixtureStore.destroyData ));
mockServer.on("messages create", toListener( fixtureStore.createData  ));
mockServer.on("messages update", toListener( fixtureStore.updateData  ));

There is also a helper storeToListeners to create all listeners at once:

var listeners = fixtureSocket.storeToListeners(messagesStore);
mockServer.on({
    "messages find": listeners.getListData,
    "messages get": listeners.getData,
    "messages remove": listeners.destroyData,
    "messages create": listeners.createData,
    "messages update": listeners.updateData
});

Now lets implement a CRUD model on our client. We define that all our ACK callbacks take an error as the first argument, and data as the second one.

var socket = io("localhost");

socket.emit("messages find", {rank: "good"}, function(err, response){
  if (err){
    console.log("Error: ", err);
    return;
  }
  console.log(`We found ${response.count} good items", response.data);
  assert.equal(response.count, 3)
});

Now lets test the rest of the methods:

socket.emit("messages get", {id: 1}, function(err, data){s
  assert.deepEqual(data, {id: 1, title: "One"}, "received the item");
});
socket.emit("messages update", {id: 2, title: "TwoPlus"}, function(err, data){
  assert.deepEqual(data, {id: 2, title: "TwoPlus"}, "received the updated item");
});
socket.emit("messages get", {id: 999}, function(err, data){
  assert.deepEqual(err, {error: 404, message: "no data"}, "received 404 when looking for a non-existent item id");
});