茉莉花钟的工作原理是什么?

How jasmine clock works?(茉莉花钟的工作原理是什么?)

问题描述

我不想花几个小时阅读代码来找到相关部分，但我很好奇 jasmine 如何实现它的时钟.它的有趣之处在于它可以使用同步测试代码来测试异步代码.AFAIK，使用当前支持 ES5 的 node.js，这是不可能的(异步函数在 ES7 中定义).它是否使用 estraverse 之类的东西解析 js 代码并从同步代码构建异步测试?

I don't want to read code for hours to find the relevant part, but I am curious how jasmine implements its clock. The interesting thing with it is that it can test async code with sync testing code. AFAIK, with the current node.js, which supports ES5, this is not possible (async functions are defined in ES7). Does it parse the js code with something like estraverse and build an async test from the sync one?

只是我所说的一个例子:

Just an example of what I am talking about:

it("can test async code with sync testing code", function () {
    jasmine.clock().install();

    var i = 0;
    var asyncIncrease = function () {
        setTimeout(function () {
            ++i;
        }, 1);
    };

    expect(i).toBe(0);
    asyncIncrease();
    expect(i).toBe(0);
    jasmine.clock().tick(2);
    expect(i).toBe(1);

    jasmine.clock().uninstall();
});

这里 expect(i).toBe(1); 应该在回调中.

In here the expect(i).toBe(1); should be in a callback.

推荐答案

install() 函数实际上将 setTimeout 替换为 jasmine 让您可以更好地控制的模拟函数.这使它同步，因为没有完成实际的等待.相反，您可以使用 tick() 函数手动将其向前移动，该函数也是同步的.

The install() function actually replaces setTimeout with a mock function that jasmine gives you more control over. This makes it synchronous, because no actual waiting is done. Instead, you manually move it forward with the tick() function, which is also synchronous.

查看源代码:https://github.com/jasmine/jasmine/blob/ce9600a3f63f68fb75447eb10d62fe07da83d04d/src/core/Clock.js#L21

假设您有一个内部设置超时 5 小时的函数.Jasmine 只是替换了该 setTimeout 调用，以便在您调用 tick() 时调用回调，以便内部计数器达到或超过 5 小时标记.很简单！

Suppose you had a function that internally set a timeout of 5 hours. Jasmine just replaces that setTimeout call so that the callback will be called when you call tick() so that the internal counter reaches or exceeds the 5 hour mark. It's quite simple!

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