如何模拟Mocha测试中的时间流逝，以便调用setTimeout回调？ [英] How can I simulate the passing of time in Mocha tests so that setTimeout callbacks are called?

问题描述

我需要测试依赖于 setTimeout 的JavaScript代码才能执行定期任务。我如何从我的Mocha测试中模拟时间的流逝，以便调用setTimeout回调？

我基本上要求的功能类似于Jasmine的模拟时钟，它允许您将JavaScript时间推进许多刻度。

解决方案

我发现Sinon.JS支持通过sinon.useFakeTimers操作JavaScript时钟，如假定时器文档。这是完美的，因为我已经将Sinon用于嘲弄目的，我想Mocha本身不支持这一点，因为它更像是一个模拟库。

<这是一个使用Mocha / Chai / Sinon的例子：

  var clock; 
 beforeEach（function（）{
 clock = sinon.useFakeTimers（）; 
}）; 
 
 afterEach（function（）{
 clock.restore（）; 
}）; 
 
 it（应该在500 ms后超时，function（）{
 var timedOut = false; 
 setTimeout（function（）{
 timedOut = true; 
}，500）; 
 
 timedOut.should.be.false; 
 clock.tick（510）; 
 timedOut.should.be.true; 
}）; 
  

I need to test JavaScript code that relies on setTimeout in order to perform periodic tasks. How can I from my Mocha tests simulate the passing of time so that setTimeout callbacks gets called?

I am basically asking for functionality similar to Jasmine's Mock Clock, which allows you to advance JavaScript time by a number of ticks.

解决方案

I found out that Sinon.JS has support for manipulating the JavaScript clock, via sinon.useFakeTimers, as described in its Fake Timers documentation. This is perfect since I already use Sinon for mocking purposes, and I guess it makes sense that Mocha itself doesn't support this as it's more in the domain of a mocking library.

Here's an example employing Mocha/Chai/Sinon:

var clock;
beforeEach(function () {
     clock = sinon.useFakeTimers();
 });

afterEach(function () {
    clock.restore();
});

it("should time out after 500 ms", function() {
    var timedOut = false;
    setTimeout(function () {
        timedOut = true;
    }, 500);

    timedOut.should.be.false;
    clock.tick(510);
    timedOut.should.be.true;
});

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