尽管尚未实现验证,但Rails教程测试仍通过

我在听迈克尔·哈特尔的轨道教程( https://www.railstutorial.org/book/following_users#code-relationship_validations )我试图理解为什么我认为应该失败的测试通过了。

我有一个 Relationship 模型。看起来是这样的:

class Relationship < ApplicationRecord
    belongs_to :follower, class_name: "User"
    belongs_to :followed, class_name: "User"
    # validates :follower_id, presence: true
    # validates :followed_id, presence: true
end

我添加了以下测试:

require 'test_helper'

class RelationshipTest < ActiveSupport::TestCase

  def setup
    @relationship = Relationship.new(follower_id: users(:michael).id,
                                     followed_id: users(:archer).id)
  end

  test "should be valid" do
    assert @relationship.valid?
  end

  test "should require a follower_id" do
    @relationship.follower_id = nil
    assert_not @relationship.valid?
  end

  test "should require a followed_id" do
    @relationship.followed_id = nil
    assert_not @relationship.valid?
  end
end

相关部分 schema.rb 如下所示:

create_table "relationships", force: :cascade do |t|
  t.integer "follower_id"
  t.integer "followed_id"
  t.datetime "created_at", null: false
  t.datetime "updated_at", null: false
  t.index ["followed_id"], name: "index_relationships_on_followed_id"
  t.index ["follower_id", "followed_id"], name: "index_relationships_on_follower_id_and_followed_id", unique: true
  t.index ["follower_id"], name: "index_relationships_on_follower_id"
end

尽管已经对验证进行了注释,但测试仍然通过。据我所知,最后两个断言应该失败,因为没有任何验证可以防止将任一列设置为零。为什么没有验证就通过了?是因为两列都有索引吗?