我该如何测试rails cache功能

Question

这是我的Tag模型,我不知道如何测试Rails.cache功能.

class Tag < ActiveRecord::Base
  class << self
    def all_cached
      Rails.cache.fetch("tags.all", :expires_in => 3.hours) do
        Tag.order('name asc').to_a
      end
    end
    def find_cached(id)
      Rails.cache.fetch("tags/#{id}", :expires_in => 3.hours) do
        Tag.find(id)
      end
    end
  end

  attr_accessible :name
  has_friendly_id :name, :use_slug => true, :approximate_ascii => true
  has_many :taggings #, :dependent => :destroy
  has_many :projects, :through => :taggings
end

你知道怎么测试吗？

Answer 1

嗯,首先,你不应该真正测试框架.Rails的缓存测试表面上可以为您提供.也就是说,看看这个答案,你可以使用一个小帮手.您的测试看起来像是这样的:

describe Tag do
  describe "::all_cached" do
    around {|ex| with_caching { ex.run } }
    before { Rails.cache.clear }

    context "given that the cache is unpopulated" do
      it "does a database lookup" do
        Tag.should_receive(:order).once.and_return(["tag"])
        Tag.all_cached.should == ["tag"]
      end
    end

    context "given that the cache is populated" do
      let!(:first_hit) { Tag.all_cached }

      it "does a cache lookup" do
        before do
          Tag.should_not_receive(:order)
          Tag.all_cached.should == first_hit
        end
      end
    end
  end
end

这实际上并没有检查缓存机制 - 只是#fetch没有调用块.它很脆弱并且与获取块的实现相关联,因此要注意它将成为维护债务.