在第一个方法采用参数的情况下，如何使用Rspec“期望"方法链?

问题描述

我在ruby模型中有一个方法调用，如下所示:

I have a method call in a ruby model that looks like the following:

Contentful::PartnerCampaign.find_by(vanityUrl: referral_source).load.first

在模型的spec.rb文件中，我试图模拟该调用并通过传入参数来获取值.但是我很难弄清楚调用它的正确方法.

Within the models spec.rb file, I'm trying to mock that call and get a value by passing in a param. But I'm having trouble figuring out the correct way of calling it.

在我的spec.rb文件的顶部，

At the top of my spec.rb file I have:

 let(:first_double) {
   double("Contentful::Model", fields {:promotion_type => "Promotion 1"})
 }

在describe块中，我尝试了以下操作:

Within the describe block I've tried the following:

expect(Contentful::PartnerCampaign).to receive_message_chain(:find_by, :load, :first).
                                       and_return(first_double)

expect(Contentful::PartnerCampaign).to receive_message_chain(:find_by, :load, :first).with(vanityUrl: 'test_promo_path').
                                       and_return(first_double)

expect(Contentful::PartnerCampaign).to receive_message_chain(:find_by => vanityUrl: 'test_promo_path', :load, :first).
                                       and_return(first_double)

您可能会猜到，这些都不起作用.有人知道做这种事情的正确方法吗?甚至有可能吗?

As you can probably guess, none of these are working. Does anyone know the correct way to do this sort of thing? Is it even possible?

推荐答案

一般来讲，我不希望使用存根链，因为它们通常表示您违反了《得墨meter耳法律》 .但是，如果需要的话，这就是我模拟该序列的方式:

Generally speaking, I prefer not to use stub chains, as they are often a sign that you are violating the Law of Demeter. But, if I had to, this is how I would mock that sequence:

let(:vanity_url) { 'https://vanity.url' }
let(:partner_campaigns) { double('partner_campaigns') }
let(:loaded_partner_campaigns) { double('loaded_partner_campaigns') }

let(:partner_campaign) do
  double("Contentful::Model", fields {:promotion_type => "Promotion 1"}
end

before do
  allow(Contentful::PartnerCampaign)
    .to receive(:find_by)
    .with(vanity_url: vanity_url)
    .and_return(partner_campaigns)

  allow(partner_campaigns)
    .to receive(:load)
    .and_return(loaded_partner_campaigns)

  allow(loaded_partner_campaigns)
    .to receive(:first)
    .and_return(partner_campaign)
end

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