做 model 的时候，在数据库层约束了 null 是 false，然后又在 model 本身加上了 validates presence: true。现在写 test，当尝试为其赋空值时，期望得到这个 record 没有添加成功，不想 test 直接给了 error，说 ActiveRecord::RecordInvalid: Validation failed: Assetnum（就是那个不能为空的字段）can't be blank。 请问这样的测试应该怎么写？谢谢！ 贴代码： 先建表，

create_table "hardwares", force: :cascade do |t|
    t.string   "AssetNum",        null: false
  #此处省略若干其他字段
    t.datetime "created_at",      null: false
    t.datetime "updated_at",      null: false
  end

然后做 model

class Hardware < ActiveRecord::Base
  validates :AssetNum, presence: true
end

create 动作是酱紫的

class HardwaresController < ApplicationController
  def new
    @hardware = Hardware.new
  end

  def create
    @hardware = Hardware.new(hardware_params)
    @hardware.save!
    redirect_to @hardware
  end
  private
    def hardware_params
      params.require(:hardware).permit(:AssetNum, :CPU, :Disk1Size, :Disk1Num,
                                       :Disk2Size, :Disk2Num, :Disk3Size,
                                       :Disk3Num, :Mem1Size, :Mem1Num, :Mem2Size,
                                       :Mem2Num, :BuyingTime, :DeployingTime,
                                       :Position, :ServerType, :ServerModel,
                                       :ServiceNum, :QuickServiceNum )
    end
end

程序到这里都 OK，可以正常的创建，于是我做了一个 test 来检测提交空值的 AssetNum 会不会创建这个记录，如下

class CreateHardwareTest < ActionDispatch::IntegrationTest

  def setup
    @h1 = hardwares(:h1)
  end

test "create hardware with invalid information" do

    assert_no_difference 'Hardware.count' do
      post hardwares_path, hardware: {
                             AssetNum: "" ,
                             CPU: @h1.CPU ,
                             Disk1Size: @h1.Disk1Size ,
                             Disk1Num: @h1.Disk1Num ,
                             Mem1Size: @h1.Mem1Size ,
                             Mem1Num:  @h1.Mem1Num ,
                             BuyingTime: @h1.BuyingTime ,
                             DeployingTime: @h1.DeployingTime ,
                             Position: @h1.Position ,
                             ServerType: @h1.ServerType ,
                             ServerModel: @h1.ServerModel ,
                             ServiceNum: @h1.ServiceNum ,
                             QuickServiceNum: @h1.QuickServiceNum
                         }
    end
  end
end

理论上来说 OK 的，但是跑测试的结果却是：

ERROR["test_create_hardware_with_invalid_information", CreateHardwareTest, 2015-07-29 08:39:36 +0800]
 test_create_hardware_with_invalid_information#CreateHardwareTest (1438130376.94s)
ActiveRecord::RecordInvalid:         ActiveRecord::RecordInvalid: Validation failed: Assetnum can't be blank
            app/controllers/hardwares_controller.rb:13:in `create'
            test/integration/create_hardware_test.rb:39:in `block (2 levels) in <class:CreateHardwareTest>'
            test/integration/create_hardware_test.rb:38:in `block in <class:CreateHardwareTest>'

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求怎么破？谢谢！