Jasmine 的 toThrow 匹配器是否需要将参数包装在匿名函数中?

2022-01-11 00:00:00 jasmine javascript

https://github.com/pivotal/jasmine/wiki 上的文档/Matchers 包括以下内容:

The documentation at https://github.com/pivotal/jasmine/wiki/Matchers includes the following:

expect(function(){fn();}).toThrow(e);

如 this question 中所述，下面的不工作，因为我们想传递一个函数对象给expect而不是调用fn():

As discussed in this question, the following does not work, because we want to pass a function object to expect rather than the result of calling fn():

expect(fn()).toThrow(e);

以下是否有效?

expect(fn).toThrow(e);

如果我使用方法 doIt 定义了一个对象 thing，那么以下操作是否有效?

If I've defined an object thing with a method doIt, does the following work?

expect(thing.doIt).toThrow(e);

(如果是这样，有没有办法将参数传递给 doIt 方法?)

(If so, is there a way to pass arguments to the doIt method?)

从经验上看，答案似乎是肯定的，但我不太相信我对 JavaScript 作用域的理解足以确定.

Empirically the answer seems to be yes, but I don't trust my understanding of JavaScript scoping quite enough to be sure.

推荐答案

我们可以使用 ECMAScript 5.这适用于最新版本的浏览器，您可以通过自己定义函数来修补旧版浏览器.Mozilla 开发者网络Mozilla Developer Network.

We can do away with the anonymous function wrapper by using Function.bind, which was introduced in ECMAScript 5. This works in the latest versions of browsers, and you can patch older browsers by defining the function yourself. An example definition is given at the Mozilla Developer Network.

下面是一个例子，说明如何将 bind 与 Jasmine 一起使用.

Here's an example of how bind can be used with Jasmine. 

describe('using bind with jasmine', function() {

    var f = function(x) {
        if(x === 2) {
            throw new Error();
        }
    }

    it('lets us avoid using an anonymous function', function() {
        expect(f.bind(null, 2)).toThrow();
    });

});

提供给 bind 的第一个参数在调用 f 时用作 this 变量.f 在调用时会传递任何附加参数.这里 2 作为它的第一个也是唯一的参数被传递.

The first argument provided to bind is used as the this variable when f is called. Any additional arguments are passed to f when it is invoked. Here 2 is being passed as its first and only argument.

相关文章