我应该等待期望(<async>) 条件吗 [英] Should I await expect(<async>) conditions

问题描述

https://www.protractortest.org/#/async-await显示了在量角器中使用 async/await 的示例，但包含以下行:

https://www.protractortest.org/#/async-await shows an example of using async/ await in protractor, but includes the line:

    expect(await greeting.getText()).toEqual('Hello Julie!');

但我不明白这怎么可能是正确的:如果 greeting.getText() 是异步的(由 await 指示)，那么直到该行完成后才能知道文本.不是:

But I don't understand how that can be correct: if the greeting.getText() is async (indicated by the await), then the text won't be known until after that line has completed. Isn't:

    await expect(await greeting.getText()).toEqual('Hello Julie!');

因此，在继续之前，我们肯定会等待获取(并检查)文本.在这个例子中，它并不太重要(假设执行了期望检查)，但一般来说，是否存在通过进一步操作重新排序 getText() 的风险(例如，这可能会将其从 DOM 中删除).

So we definitely wait for the text to be obtained (and checked) before we move on. In this example, it's not too important (assuming the expect check does execute), but in general, is there any risk of re-ordering the getText() with further operations (which may remove it from the DOM, for example).

如果它只是基于浏览器的异步操作在实践中是否安全，因为它们无论如何都是串行执行的(因此 getText() 将在后续操作之前完成?

Is it in practice safe if it's only browser-based async operations, as they execute serially anyway (so the getText() will complete before a subsequent operation?

大概如果我们包含基于非浏览器的异步操作(例如，我们向服务器发出 http 请求)，则无法保证排序，因此最佳实践是编写 'await expect(...).toX(...)' (即使期望表达式不是异步的也是安全的).

Presumably if we included non-browser based async operations (e.g. we did a http request to a server), then the ordering wouldn't be guaranteed, so best practice would be to write 'await expect(...).toX(...)' (which is safe even if the expect expression is not async).

当然，尽管如此，我们最终在几乎每一行的开头都有等待"，这看起来有点难看.

Of course, with all that, we end up with 'await' on the beginning of nearly every line, which looks a bit ugly.

推荐答案

Protractor 引入 await 后真的很简单，不需要复杂化了

Protractor is really simple after the introduction of await, don't need to complicate it

首先在配置文件中禁用 selenium 控制流，只需在配置文件中添加这一行:

First disable selenium control flow in config file, just add this line in config file:

SELENIUM_PROMISE_MANAGER: false

https://www.protractortest.org/#/control-flow

目前正在测试使用中:

  it('should find an element by text input model', async function() {
    await browser.get('app/index.html#/form');

    var username =element(by.model('username'));
    await username.clear();
    await username.sendKeys('Jane Doe');

    var name = element(by.binding('username'));

    expect(await name.getText()).toEqual('Jane Doe');

  });

请注意，我没有使用等待

Note that i am not using await for

 var name = element(by.binding('username'));

这是因为在量角器中，除非您在其上调用方法，否则不会触发查找元素操作

This is because in protractor the find element action is not triggered unless you call a method on it

所以你不必在那里使用 await

so you don't have to use await there

除非你调用任何方法，否则你不会得到 element not found .

you won't get element not found unless you call any method on it .

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