如何使用mocha.js测试多个异步进程事件

Question

我尝试用mocha.js测试一些异步进程事件。默认情况下，it方法在done调用后执行synchronious。使用mocha.js测试多个异步进程的策略是什么

describe('Game', function(done){
    var game = new Simulation.Game();
    this.timeout(5000);

    it('should start', function(done){
        game.on('start', function() {
            done();
        });
    });

    it('should log', function(done){
        game.on('log', function() {
            done();
        });
    });

    it('should end', function(done){
        game.on('end', function() {
            done();
        });
    });

    game.start();
});

Answer 1

您可能需要使用the ()钩子来正确设置测试。试试这个：

describe('Game', function(){
    var game;
    this.timeout(5000);

    before(function(before_done) {
        game = new Simulation.Game();
        game.start();
        before_done();
    };        

    it('should start', function(done){
        game.on('start', function() {
            done();
        });
    });

    it('should log', function(done){
        game.on('log', function() {
           done();
        });
    });

    it('should end', function(done){
        game.on('end', function() {
           done();
        });
      });
});

Answer 2

一种方法是使用promises来捕获游戏回调的结果：

describe('Game', function(done){
    var started, logged, ended;

    // Wrapping the initialization code in a before() block
    // allows subsequent describe blocks to be run if an
    // exception is thrown.
    before(function () {
        var game = new Simulation.Game();
        var game_on = function (event) {
            return new Promise(function (resolve, reject) {
                game.on(event, function () {
                    resolve();
                });
            });
        };

        started = game_on('start');
        logged = game_on('log');
        ended = game_on('end');

        game.start();
    });

    this.timeout(5000);

    it('should start', function(){
        return started;
    });

    it('should log', function(){
        return logged;
    });

    it('should end', function(){
        return ended;
    });
});

game_on函数为调用回调时解析的每个事件创建新的promises。由于游戏尚未开始，事件处理程序已正确注册。

在it块中，promises只是返回since mocha will pass the test when they resolve。如果它们不能解决，它们的测试将拒绝，并显示超时错误。