问题描述

我使用 jasmine 运行并等待测试异步操作.一切正常，但我不太确定幕后发生了什么.

I use jasmine runs and wait to test asynchronous operations. Everything works fine but I'm not quite sure what goes on behind the scenes.

jasmine 文档说明了以下示例，我在其中添加了三个日志语句.

The jasmine documentation states the following example to which I added three log statement.

describe("Asynchronous specs", function() {
  var value, flag;

  it("should support async execution of test preparation and exepectations", function() {

    runs(function() {
      flag = false;
      value = 0;

      setTimeout(function() {
        flag = true;
      }, 500);
    });

    waitsFor(function() {
      value++;
      if(flag) {
          console.log("A");
      }
      return flag;
    }, "The Value should be incremented", 750);

    console.log("B");

    runs(function() {
      console.log("C");
      expect(value).toBeGreaterThan(0);
    });
  });
});

});

第一个 runs 和 waitsFor 对我来说非常清楚.Runs 启动异步操作，waitsFor 等待条件.

The first runs and waitsFor are perfectly clear to me. Runs starts an asynchronous operation and waitsFor waits for a condition.

但是我不明白为什么第二个 runs 直到 waitsFor 完成才开始.waitsFor 不是阻塞调用.

However I do not understand why the second runs does not start until the waitsFor is finished. The waitsFor is not a blocking call.

我的猜测是 waitsFor 会隐式阻止任何后续的 runs 调用，直到它完成.是这样吗?

My guess is that waitsFor implicitly blocks any following runs call until it is finished. Is this so?

我的证据是 console.log 语句输出:

My evidence is that the console.log statements output:

B A C

但如果 waitsFor 真的会阻塞它应该是

But if waitsFor would really block it should be

A B C

推荐答案

waitsFor 会阻塞，直到它等待的条件满足或超时.

waitsFor does block until the conditions it's waiting for are met or it times out.

来自 jasmine 文档:waitsFor() 提供了一个更好的接口，用于暂停你的规范，直到完成其他一些工作.Jasmine 将等到提供的函数返回 true，然后再继续下一个块.".

From the jasmine docs: "waitsFor() provides a better interface for pausing your spec until some other work has completed. Jasmine will wait until the provided function returns true before continuing with the next block.".

链接的文档也有一个更清晰的示例或 waitsFor.

The linked docs also have a slightly clearer example or waitsFor.

编辑:啊，我明白你的意思了.waitsFor 不会阻塞未包含在 runs、waitsFor 等中的 JS.

EDIT: Ah I see what you mean now. waitsFor won't block JS that isn't wrapped in runs, waitsFor, ect.

jasmine 正在做的是获取通过 runs 或 waitsFor 传递给它的函数，如果 jasmine 当前没有等待，它会立即执行该函数.如果它正在等待，它在等待完成之前不会调用它.

What jasmine is doing is taking the function passed to it via runs or waitsFor and if jasmine is not currently waiting, it executes the function immediately. If it is waiting, it doesn't call it until it's finished waiting.

这不会停止 console.log，因为它已被传递给 jasmine，因此 jasmine 无法阻止它立即执行.

That doesn't stop the console.log as it's been passed to jasmine so jasmine can't prevent it from being executed straight away.

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