我該如何測試rails緩存功能

Question

這是我的Tag模型，我不知道如何測試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 

你知道怎麼會被測試嗎？

Answer 1

嗯，首先，你不應該真的在測試框架。 Rails的緩存測試表面上覆蓋了你。也就是說，見this answer你可以使用一個小助手。那麼你的測試將類似於：

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 

這並不實際檢查緩存機制 - 剛纔說的#fetch塊不被調用。它很脆弱，並與獲取塊的實現有關，所以要小心，因爲它會成爲維護債務。