问题描述

有没有办法在 Jasmine expect() 失败时打印自定义错误消息?

Is there a way to print a custom error message when a Jasmine expect() fails?

例如，对于端到端测试，我有一组网页，我使用一个测试转到每个 URL 并断言每个页面上都存在一个元素.我知道我可以将每个 expect() 放入单独的测试中，但我宁愿遍历数组并在失败时记录页面 URL.

As an example, for end to end testing I have an array of web pages and I use one test to go to each URL and assert an element exists on each page. I know I can put every expect() into a separate test, but I'd rather iterate through the array and log the page URL on failure.

推荐答案

更新

我看到人们仍在寻找这个.Jasmine 团队后来提供的信息是，expect 中有一个未记录的功能 - 您可以包含自定义失败消息并且它可以正常工作:

I see people still are finding this. Later information from the Jasmine team is that there is an undocumented feature on the expect - you can include a custom failure message and it just works:

expect( fields[i].element.exists() ).toEqual(true, field[i].name + ' is expected to exist');

这正是我最初想要的.

原答案如下:

我今天一直在寻找这个，并在这里发表评论:https://github.com/adobe/brackets/issues/2752

I've been looking for exactly this today, and put a comment here: https://github.com/adobe/brackets/issues/2752

已经讨论的语法是对 Jasmine 的扩展，允许添加因为 - 所以你可以写:

The syntax that has been discussed is an extension to Jasmine to permit a because to be added - so you'd be able to write:

expect( fields[i].element.exists() ).toEqual(true).because( field[i].name + 'is expected to exist');

几年后仍在讨论中，可能不会实现.我发现的另一种方法是创建自定义匹配器.一般来说，我认为我不鼓励使用自定义匹配器，但不确定你是否用它覆盖了所有基础，但在这种情况下，我们实际上是在检查真/假值，所以匹配器并不太可怕.

That is still being discussed after a few years, and may not come to fruition. Another way that I've found to do this is to create a custom matcher. In general I think I'd discourage a custom matcher without being sure you're covering all the bases with it, but in this case we're really checking a true/false value, so the matcher isn't too scary.

我们可以使用 beforeEach 创建自定义匹配器:

We can create the custom matcher with a beforeEach:

beforeEach(function() {
  var matchers = {
    toEqualBecause: function( value, message ) {
      this.message = function() {
        return "Expected '" + this.actual + "' to equal '" + value + "' because " + message;  
      };

      return this.actual == value;  
    }
 };

  this.addMatchers(matchers);
});

然后我们可以使用这个匹配器来发送一条带有我们失败的消息:

We can then use this matcher to put a message with our failures as such:

expect( field[i].element.exists() ).toEqualBecause( true, field[i].name );

这将给出包括字段名称在内的失败输出:

Which will give a failure output including the field name as such:

Expected 'false' to equal 'true' because account_name

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