Use

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

import io from "socket.io-client";
import fixtureSocket from "can-fixture-socket";
const 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:

const 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.

import fixture from "can-fixture";

// First, lets create fixture store:
const 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:
import io from "socket.io-client";

import fixtureSocket from "can-fixture-socket";
const 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:

const 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.

const 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"
    );
} );