轨道测试的异常行为

Question

我有一个名为ticket的模型如下：

ActiveRecord::Schema.define(version: 20151231072055) do

  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"
  create_table "tickets", force: :cascade do |t|
    t.string   "movie_name"
    t.integer  "price"
    t.boolean  "is_3d"
    t.string   "theatre_name"
    t.string   "seller_name"
    t.string   "seller_email"
    t.string   "seller_mobile"
    t.string   "preferred_places"
    t.datetime "created_at",       null: false
    t.datetime "updated_at",       null: false
    t.datetime "date_and_time"
  end

end

我试图验证所有字段的存在，因此我对我的票证模型进行了以下测试：

require 'test_helper'

class TicketTest < ActiveSupport::TestCase
    def setup
        @ticket = tickets(:one)
    end

    def teardown
        @ticket = nil
    end

  test 'should not save ticket without movie name' do
    @ticket.movie_name = nil
    assert_not(@ticket.save, 'Saved the ticket without movie name')
  end

  test 'should not save ticket without price' do
    @ticket.price = nil
    assert_not(@ticket.save, 'Saved the ticket without price')
  end

    test 'should not save ticket without theatre name' do
    @ticket.theatre_name = nil
    assert_not(@ticket.save, 'Saved the ticket without theatre name')
  end

    test 'should not save ticket without seller name' do
    @ticket.seller_name = nil
    assert_not(@ticket.save, 'Saved the ticket without seller name')
  end

  test 'should not save ticket without seller email' do
    @ticket.seller_email = nil
    assert_not(@ticket.save, 'Saved the ticket without seller email')
  end

  test 'should not save ticket without seller mobile' do
    @ticket.seller_mobile = nil
    assert_not(@ticket.save, 'Saved the ticket without seller mobile')
  end

  test 'should not save ticket without preferred places' do
    @ticket.preferred_places = nil
    assert_not(@ticket.save, 'Saved the ticket without preferred places')
  end

    test 'should not save ticket without date and time' do
    @ticket.date_and_time = nil
    assert_not(@ticket.save, 'Saved the ticket without date and time')
  end  

  test 'should not save ticket without 3D status' do
    @ticket.is_3d = nil
    assert_not(@ticket.save, 'Saved the ticket without 3D status')
  end

end

我在我的故障单模型中编写了以下代码，以便通过测试：

class Ticket < ActiveRecord::Base
    validates_presence_of :is_3d
end

这使得所有测试用例都能通过。我一直注意到的是，如果我单独检查is_3d的存在，一切都在通过（异常），如果我单独检查是否存在任何其他字段，那么单独对该特定字段的测试正在通过（这是正常的）。