如何将 rspec 与 before_validation 一起使用

我无法理解如何正确使用 before_validation 回调与 Rspec。

模型/类别.rb

class Category < ActiveRecord::Base 
    validates_presence_of :name, :permalink
    before_validation :generate_permalink

    private
    def generate_permalink
        self.permalink = Russian.translit(name).parameterize if permalink.blank?
    end
end

类别_规格.rb

describe Category do
    it { should validate_presence_of(:name) }   
    it { should validate_presence_of(:permalink) }
    it "should generate permalink" do
        category = build(:category, name: "Category name", permalink: "")
        category.valid?
        category.permalink.should eq "category-name" 
    end
end

and 工厂/类别.rb

FactoryGirl.define do
  factory :category do
    name "Category name"
    permalink "category-name"
  end
end

对于前两个测试，我遇到了错误：

undefined method `scan' for nil:NilClass

您可以检查实例的验证，而不是类本身的验证：

it "should be invalid without a name" do
  category = build(:category, name: "some name", permalink: "some link")
  expect{ category.name = nil }.to change{ category.valid? }.to false
end

对代码中永久链接存在的验证过多。 这before_validation回调将在验证之前为永久链接提供非空值。这就是为什么永久链接的验证永远不会失败的原因。