模拟`Resolv::DNS.open`麻烦

Question

我试图使用MiniTest/Mocks来模拟下面的代码。但是当我运行测试时，我总是会发现这个错误。

Minitest::Assertion: unexpected invocation: #<Mock:0x7fa76b53d5d0>.size()
unsatisfied expectations:
- expected exactly once, not yet invoked: #<Mock:0x7fa76b53d5d0>.getresources("_F5DC2A7B3840CF8DD20E021B6C4E5FE0.corwin.co", Resolv::DNS::Resource::IN::CNAME)
satisfied expectations:
- expected exactly once, invoked once: Resolv::DNS.open(any_parameters)

正在测试的代码

txt = Resolv::DNS.open do |dns|
            records = dns.getresources(options[:cname_origin], Resolv::DNS::Resource::IN::CNAME)
          end
          binding.pry
          return (txt.size > 0) ? (options[:cname_destination].downcase == txt.last.name.to_s.downcase) : false

我的测试

::Resolv::DNS.expects(:open).returns(dns = mock)
  dns.expects(:getresources)
     .with(subject.cname_origin(true), Resolv::DNS::Resource::IN::CNAME)
     .returns([Resolv::DNS::Resource::IN::CNAME.new(subject.cname_destination)])
     .once

Answer 1

现在您正在测试Resolv::DNS接收到的open返回您的mock，但是由于您似乎试图测试dns模拟是否正在接收消息，所以需要对该方法进行存根，并为其提供要生成的对象。

试一试：

 dns = mock 
 dns.expects(:getresources)
   .with(subject.cname_origin(true), Resolv::DNS::Resource::IN::CNAME)
   .once
 ::Resolv::DNS.stub :open, [Resolv::DNS::Resource::IN::CNAME.new(subject.cname_destination)], dns do 
   # whatever code actually calls the "code being tested" 
 end 
 dns.verify

存根的第二个参数是存根返回值，而stub的第三个参数是将生成的块代替原来生成的块。

在RSpec中，语法稍微简单一些(而且更有语义)，因此：

 dns = double 
 allow(::Resolv::DNS).to receive(:open).and_yield(dns) 
 expect(:dns).to receive(:getresources).once
   .with(subject.cname_origin(true), Resolv::DNS::Resource::IN::CNAME)
   .and_return([Resolv::DNS::Resource::IN::CNAME.new(subject.cname_destination)])
  # whatever code actually calls the "code being tested" 

Answer 2

您可以使用DnsMock编写更具可读性的集成测试，而不是对代码的某些部分进行顽固/嘲弄：https://github.com/mocktools/ruby-dns-mock。