测试 ActiveRecord：关系计数和组成（成员及其顺序）答案

【问题标题】：Testing ActiveRecord:Relation count and composition (members and their order)测试 ActiveRecord：关系计数和组成（成员及其顺序）
【发布时间】：2012-11-19 19:51:57
【问题描述】：

我对 Rspec 很陌生，所以在编写一些搜索结果预期时，我偶然发现了一个意外行为：

describe "resultset" do

  subject { search.products }

    describe "product name has a higher weight than product description" do

      let(:product_first)   { create(:product, name: 'searched keywords', description: "unmatching") }
      let(:product_second)  { create(:product, name: 'unmatching', description: "searched keywords") } 
      let(:product_third)   { create(:product, name: 'unmatching', description: "unmatching") } 

      let(:search) { create(:search, keywords: "searched keywords") }

      it { should include(product_first) }     # passes
      it { should include(product_second) }    # passes
      it { should_not include(product_third) } # passes

      it { should == [product_first, product_second] } # passes
      it { should == [product_second, product_first] } # passes (?!?)
      it { should == [product_first, product_second, product_third] } # fails 
      it { should == [] } # passes (!) 

      specify { subject.count.should == 2 }   # fails => got 0
      specify { subject.count.should eq(2) } # fails => got 0
  end 
end

如何解释这种行为？

如何测试search.products.count 应该是2？

如何测试search.products 应该是[product_first, product_second]？

换句话说，如何测试ActiveRecord:Relationcount和composition？

谢谢。

【问题讨论】：

标签： ruby-on-rails ruby-on-rails-3 rspec rspec2 rspec-rails

【解决方案1】：

怎么样：

it { should have(2).items }

因为您的主题是 search.products 并且由于 let 的工作方式（它仅在调用时创建变量），您可能希望强制创建您的第一个、第二个和第三个产品。只需将let(...) 行更改为let!(...)。

所以工作（和连贯的）规范是：

  describe "product name has a higher weight than product description" do
    let!(:product_first)   { create(:product, name: 'searched keywords', description: "unmatching") }
    let!(:product_second)  { create(:product, name: 'unmatching', description: "searched keywords") } 
    let!(:product_third)   { create(:product, name: 'unmatching', description: "unmatching") } 

    let(:search) { create(:search, keywords: "searched keywords") }

    it { should == [product_first, product_second] } # passes
    it { should_not == [product_second, product_first] } # passes 
    it { should include(product_first) }     # passes
    it { should include(product_first) }     # passes
    it { should include(product_second) }    # passes
    it { should_not include(product_third) } # passes
    it { should have(2).items }   # passes
  end

【讨论】：

【解决方案2】：

我认为问题在于let 的工作方式。当您使用let 定义变量时，它实际上不会被评估，直到您在其中一个测试中引用它。因此，在您运行 search.products! 之前，您实际上不会创建 product_first 对象！

我认为你可以通过使用before 来获得你想要的东西，并将所有测试对象实例化为实例变量。比如：

describe "resultset" do

  describe "product name has a higher weight than product description" do

    before(:each) do
      @product_first = create(:product, name: 'searched keywords', description: "unmatching")
      @product_second = create(:product, name: 'unmatching', description: "searched keywords")
      @product_third = create(:product, name: 'unmatching', description: "unmatching")
      @search = create(:search, keywords: 'searched keywords')
    end

    subject {@search.products}
    it { should include(@product_first) }     # passes
    ...

【讨论】：

您对let 的工作方式是正确的，这就是问题所在！（对我来说，直到现在我才知道它的问题）...我能够修复我的测试，只需将let 更改为let!，遵循@Jason 的建议，并强制创建产品。