如何使用 rspec 模拟 3.3 测试方法的救援块 [英] How do I test the rescue block of a method with rspec mocks 3.3

问题描述

这是一些rspec代码的例子，

Here is an example of some rspec code,

class User
  attr_accessor :count
  
  def initialize
    @count = 0
  end

  # sometimes raises
  def danger
    puts "IO can be dangerous..."
  rescue IOError => e
    @count += 1
  end
  
  #always raises
  def danger!
    raise IOError.new    
  rescue IOError => e
    @count += 1
  end
end

describe User do  
  describe "#danger!" do
    it "its rescue block always increases the counter by one" do
      allow(subject).to receive(:'danger!')
      
      expect {
        subject.danger!
      }.to change(subject, :count).by(1)
    end
  end

  describe "#danger" do
    context "when it rescues an exception" do
      it "should increase the counter" do
        allow(subject).to receive(:danger).and_raise(IOError)
        
        expect {
          subject.danger
        }.to change(subject, :count).by(1)
      end      
    end
  end
end

我还创建了一个 fiddle，其中包含这些测试，所以你可以让他们通过.请帮我测试一个方法的救援块！

I've also created a fiddle with these tests in it, so you can just make them pass. Please help me test the rescue block of a method!

背景:

我最初的问题是这样的:

My original question went something like this:

我有一个方法，如下所示:

I have a method, like the following:

def publish!(resource)
  published_resource = resource.publish!(current_project)

  resource.update(published: true)

  if resource.has_comments?
    content = render_to_string partial: "#{ resource.class.name.tableize }/comment", locals: { comment: resource.comment_content_attributes }

    resource.publish_comments!(current_project, published_resource.id, content)
  end

  true

  rescue Bcx::ResponseError => e
    resource.errors.add(:base, e.errors)

    raise e
  end

而且我想测试 resource.errors.add(:base, e.errors) 实际上是向资源添加错误.更一般地说，我想在一个方法中测试救援块.

And I want to test that resource.errors.add(:base, e.errors) is, in fact, adding an error to the resource. More generally, I want to test the rescue block in a method.

所以我想写这样的代码，

So I'd like to write code like,

it "collects errors" do 
  expect{ 
    subject.publish!(training_event.basecamp_calendar_event)
  }.to change(training_event.errors.messages, :count).by(1)
end

当然，这会引发一个错误，因为我在救援区再次加注.

Of course, this raises an error because I am re-raising in the rescue block.

我已经看到一些使用旧的 something.stub(:method_name).and_raise(SomeException) 的答案，但 rspec 抱怨这种语法已被弃用.我想使用 Rspec Mocks 3.3 和 allow 语法，但我遇到了困难.

I've seen a few answers that use the old something.stub(:method_name).and_raise(SomeException), but rspec complains that this syntax is deprecated. I would like to use Rspec Mocks 3.3 and the allow syntax, but I'm having a hard time.

推荐答案

我误解了 allow 语法的实际用途.所以为了让我的示例规范通过，我需要这样做:

I was misunderstanding what the allow syntax is actually for. So to make my example specs pass, I needed to do this:

describe "#danger" do
  context "when it rescues an exception" do
    it "should increase the counter" do
      allow($stdout).to receive(:puts).and_raise(IOError) # <----- here

      expect {
        subject.danger
      }.to change(subject, :count).by(1)
    end      
  end
end

我存根的这件事不是方法或主题，而是可能引发的对象.在这种情况下，我存根 $stdout 以便看跌期权将提高.

This thing that I'm stubing is not the method, or the subject, but the object that might raise. In this case I stub $stdout so that puts will raise.

这是另一个fiddle，其中规范正在通过.

Here is another fiddle in which the specs are passing.

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