如何模拟对 open-uri 的调用

Question

我有一个使用“open-uri”的邮件程序。

require 'open-uri'
class NotificationMailer < ActionMailer::Base

  def welcome(picasa_picture)
    picture = picasa_picture.content.src
    filename = picture.split('/').last
    attachments.inline[filename] = open(picture).read
    mail(
      to: 'foo@exmample.com',
      from: 'bar@example.com',
      subject: 'hi',
    )
  end
end

但是当我尝试测试该类的任何内容时，我得到了这个错误：

 SocketError:
   getaddrinfo: nodename nor servname provided, or not known

我发现了这个 SO 帖子：How to rspec mock open-uri 并认为它会有所帮助。我试了一下：

let(:pic_content) { double(:pic_content, src: 'http://www.picasa/asdf/asdf.jpeg') }
let(:picture) { double(:picture, content: pic_content) }
let(:open_uri_mock) { double(:uri_mock, read: true) }

subject { described_class.welcome(picture) }

it 'renders email address of sender' do
  subject.stub(:open).and_return(open_uri_mock)
  subject.from.should == [ sender_address ]
end

我也尝试了“should_receive”而不是“stub”，但没有帮助。

如何抑制 open-uri 'open' 方法，使其 (1) 不会尝试上网并且 (2) 不会破坏我的测试？

Answer 1

为什么不重构：

require 'open-uri'
class NotificationMailer < ActionMailer::Base

  def welcome(picasa_picture)
    picture = picasa_picture.content.src
    filename = picture.split('/').last
    attachments.inline[filename] = open_and_read(picture)
    mail(
      to: 'foo@exmample.com',
      from: 'bar@example.com',
     subject: 'hi',
    )
  end

  def open_and_read(picture)
    open(picture).read
  end

end

然后你可以存根和测试：

subject { NotificationMailer }

before do 
  subject.stub(:open_and_read).and_return(:whatever_double_you_want)
  subject.welcome(picture)
end

it 'renders email address of sender' do
  subject.from.should == [ sender_address ]
end