是否有一种干净的方式来测试Rspec中的ActiveRecord回调？

Question

假设我有以下的ActiveRecord类：

class ToastMitten < ActiveRecord::Base 
    before_save :brush_off_crumbs 
end 

有没有干净的方式来测试:brush_off_crumbs已被设置为before_save回调？

通过 “干净” 我的意思是：

1. “没有实际保存”，因为
   • 它很慢
   • 我并不需要测试ActiveRecord的正确处理一个before_save指令;我需要测试我是否正确告诉它保存之前要做什么。
2. “没有通过无证方法黑客”

我发现满足条件＃1，但不是＃2的方式：

it "should call have brush_off_crumbs as a before_save callback" do 
    # undocumented voodoo 
    before_save_callbacks = ToastMitten._save_callbacks.select do |callback| 
    callback.kind.eql?(:before) 
    end 

    # vile incantations 
    before_save_callbacks.map(&:raw_filter).should include(:brush_off_crumbs) 
end 

Answer 1

使用run_callbacks

这是不太哈克，但并不完美：

it "is called as a before_save callback" do 
    revenue_object.should_receive(:record_financial_changes) 
    revenue_object.run_callbacks(:save) do 
    # Bail from the saving process, so we'll know that if the method was 
    # called, it was done before saving 
    false 
    end 
end 

使用这种技术来测试after_save会更尴尬。