假设我有以下ActiveRecord类：
class ToastMitten < ActiveRecord::Base before_save :brush_off_crumbs end
有没有一种干净的方法来测试：brush_off_crumbs已被设置为before_save回调？
通过“干净”我的意思是：
>“没有实际储蓄”,因为
>这很慢
>我不需要测试ActiveRecord是否正确处理了before_save指令;我需要测试一下,我正确告诉它在保存之前该做什么.
>“没有黑客攻击无证方法”
我发现了一种满足标准#1而不是#2的方法：
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
解决方法
使用run_callbacks
这不那么hacky,但不完美：
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
使用这种技术测试after_save将更加尴尬.