用于检查集合以包含满足 lambda 的项目的 RSpec 匹配器 [英] RSpec matcher that checks collection to include item that satisfies lambda

问题描述

对于如何编写 RSpec 3.2.x 规范来检查列表是否包含至少一个满足条件的项目，我有点不知所措.

I am a bit at a loss as to how to write a RSpec 3.2.x spec that checks wether a list contains at least one item that satisfies a condition.

这是一个例子:

model = Invoice.new
model.name = 'test'
changes = model.changes
expect(changes).to include { |x| x.key == 'name' && x.value == 'test' }

更改列表中也会有其他(自动)更改，因此我不想验证是否只有一个特定更改，而且我也不想依赖排序 expect(changes.first)... 所以我基本上需要一种方法来指定列表中至少有一个更改满足条件.

There will be other (automated) changes in the changes list too so I don't want to verify that there is only one specific change and I also don't want to rely on ordering expect(changes.first)... so I basically need a way to specify that at least one change in the list satisfies the condition.

我可以这样做:

result = changes.any? { |x| x.key == 'name' .. }
expect(result).to eq(true)

但是 rspec 失败不会给我任何有意义的输出，所以我认为必须有一种内置的方法来匹配它.

But then the rspec failure would not give me any meaningful output so I thought there must be a built-in way to match this.

也欢迎提供有关如何构建测试的任何其他建议.

Any other suggestions on how to structure the test are also welcome.

要清楚 - 更改是 ChangeObject 的列表，因此我需要访问它们的 .key 和 .value 方法

To be clear - the changes are a list of ChangeObject so I need to access their .key and .value method

推荐答案

在 RSpec 3 中，匹配器是完全可组合的，这意味着您可以将任何实现 Ruby 的 === 协议的对象(包括匹配器！)传递给 include 它将正常工作.Ruby 1.9 中的 Lambda 实现了 === 协议，这意味着您可以这样做:

In RSpec 3, matchers are fully composable, which means you can pass any object which implements Ruby's === protocol (including a matcher!) to include and it will work properly. Lambdas in Ruby 1.9 implement the === protocol, which means you can do this:

expect(changes).to include(lambda { |x| x.key == 'name' && value == 'test' })

也就是说，这不会给您一个很好的失败消息(因为 RSpec 无法生成 lambda 的描述).我不确定您的示例中 value 的来源，但如果它打算是 x.value，您可以使用 have_attributes(或 an_object_sharing_attributes 以获得更好的可读性)匹配器:

That said, that's not going to give you a great failure message (since RSpec has no way to generate a description of the lambda). I'm not sure where value comes from in your example, but if it is intended to be x.value, you could use the have_attributes (or an_object_having_attributes for better readability) matcher:

expect(changes).to include an_object_having_attributes(key: 'name', value: 'test')

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