ruby-on-rails - Rspec / Rails：如何验证没有调用类的方法

Question

我想写这样的东西：

it 'does not invoke any MyService' do
    MyService.should_not_receive(<any method>)
    tested_method
end

我不想明确列出 MyService 的所有方法，因为这会导致脆弱的测试，如果将新方法添加到 MyService 中，可能会默默地给出误报。

Answer 1

用双精度替换实现怎么样？

it 'does not invoke any MyService' do
  original_my_service = MyService

  begin
    # Replace MyService with a double.
    MyService = double "should not receive any message"

    tested_method
  ensure
    # Restore MyService to original implementation.
    MyService = original_my_service
  end
end

如果调用 MyService 中的方法，它应该引发：

RSpec::Mocks::MockExpectationError: Double "should not receive any message" received unexpected message :some_method with (no args)

Answer 2

如果将MyService依赖项注入到对象中，则可以将其替换为没有定义方法的模拟，这样任何方法调用都会引发异常。

让我给你看一个例子：

class Manager
  attr_reader :service

  def initialize(service = MyService)
    @service = service
  end

  def do_stuff
    service.do_stuff
  end

  def tested_method
    other_stuff
  end
end

测试将是：

context "#do_stuff" do
  let(:manager) { Manager.new }

  it 'invokes MyService by default' do
    MyService.should_receive(:do_stuff)
    manager.do_stuff
  end
end

context "#tested_method" do
  let(:service) { mock("FakeService") }
  let(:manager) { Manager.new(service) }

  it 'does not invoke any service' do
    expect { manager.tested_method }.not_to raise_error
  end
end

Answer 3

it 'does not invoke MyService' do
    stub_const('MyService', double)
    tested_method
end

任何访问尝试都MyService将返回模拟的 RSpec double。由于双打在收到未显式存根的消息（并且没有被存根）时会引发错误，因此任何调用MyService都会引发错误。

https://relishapp.com/rspec/rspec-mocks/v/3-0/docs/basics/test-doubles