Writing tests

index.js

require('mocha-generators').install();
var path = require('path');
var Nightmare = require('nightmare');
var expect = require('chai').expect;

describe('AmsterdamPHP Raffler', function () {
    this.timeout(15000); // Set timeout to 15 seconds, instead of the original 2 seconds
    var url = 'http://localhost:8080',
        nightmare;

    beforeEach(function *() {
        nightmare = Nightmare({
            show: true
        });
    });

    afterEach(function *() {
        yield nightmare.end();
    });

    describe('Event List', function () {
        it('should show a list of current/past events', function *() {
            var x;
            var result = yield nightmare
                .goto(url)
                .evaluate(function (x) {
                    //return document.querySelectorAll('ul.meetups > li').length; // evaluates to 95
                    return document.querySelectorAll('ul.meetups > li');
                });

            expect(result.length).to.be.above(1); // length undefined
        });
    });

});

You also need * after the function keyword when yield is called inside the function block

so for reference: evaluate serializes return into json, hence all properties go bye bye.