Ruby on rails 使用Rails的敏捷Web开发：can'；找不到id为1的产品

行项目模型的销毁单元测试失败，错误为“找不到id为1的产品”。Rails似乎无法销毁我的行_项，因为它在从数据库获取它时抛出异常。以下是我的行项目模型：

class LineItem < ActiveRecord::Base
  belongs_to :product
  belongs_to :cart
  
  def total_price
    product.price * quantity
  end
end

编辑：以下是产品型号：

class Product < ActiveRecord::Base
  has_many :line_items
  
  before_destroy :ensure_not_referenced_by_any_line_item
  
  # Validation
  validates :title, :description, :image_url, presence: true
  validates :title, length: {
    minimum: 10,
    message: "must be at least %{count} characters long"
  }
  validates :price, numericality: { greater_than_or_equal_to: 0.01 }
  validates :title, uniqueness: true
  validates :image_url, allow_blank: true, format: {
    with: %r{\.(gif|jpg|png)$}i,
    message: 'must be a URL for GIF, JPG or PNG image.'
  }
  
  private
  
  def ensure_not_referenced_by_any_line_item
    if line_items.empty?
      return true
    else
      errors.add :base, 'Line items present'
      return false
    end
  end
end

类产品

这是rails社区中工厂通常比固定装置更受欢迎的原因之一。固定装置不会自动加载其关联，因此容易损坏。您的夹具的产品id为1，但该产品不存在

我不确定如何解决您的特定问题，但我建议您：

在测试中创建id为1的产品

创建id为1的产品夹具，并将其加载到设置中

切换到工厂（最好是这家）

编辑

如上所述，还可以使用标签引用进行关联。因此，如果您有一个名为“tv”的产品夹具，您可以删除行项目夹具的产品id字段，并将其替换为

product:tv

    Breaking!
  [1m[35m (0.1ms)[0m  SELECT COUNT(*) FROM "line_items" 
Processing by LineItemsController#destroy as HTML
  Parameters: {"id"=>"980190962"}
  [1m[36mLineItem Load (0.1ms)[0m  [1mSELECT "line_items".* FROM "line_items" WHERE "line_items"."id" = ? LIMIT 1[0m  [["id", "980190962"]]
  [1m[35mProduct Load (0.1ms)[0m  SELECT "products".* FROM "products" WHERE "products"."id" = ? LIMIT 1  [["id", 1]]
Completed 500 Internal Server Error in 3ms
  [1m[36m (0.1ms)[0m  [1mrollback transaction[0m
  [1m[35m (0.1ms)[0m  begin transaction
  [1m[36mLineItem Load (0.1ms)[0m  [1mSELECT "line_items".* FROM "line_items" WHERE "line_items"."id" = ? LIMIT 1[0m  [["id", 980190962]]
--- !ruby/object:LineItem
attributes:
  id: 980190962
  product_id: 1
  cart_id: 1
  created_at: 2012-05-25 20:37:17.000000000 Z
  updated_at: 2012-05-25 20:37:17.000000000 Z
  quantity: 1
  product_price: 

  [1m[35mProduct Load (0.2ms)[0m  SELECT "products".* FROM "products" 
---
- !ruby/object:Product
  attributes:
    id: 207281424
    title: Programming Ruby 1.9
    description: Ruby is the fastest growing and most exciting dynamic language out
      there.  If you need to get working programs delivered fast, you should add Ruby
      to your toolbox.
    image_url: ruby.png
    price: 49.5
    created_at: 2012-05-25 20:37:17.000000000 Z
    updated_at: 2012-05-25 20:37:17.000000000 Z  

class Product < ActiveRecord::Base
  has_many :line_items
  
  before_destroy :ensure_not_referenced_by_any_line_item
  
  # Validation
  validates :title, :description, :image_url, presence: true
  validates :title, length: {
    minimum: 10,
    message: "must be at least %{count} characters long"
  }
  validates :price, numericality: { greater_than_or_equal_to: 0.01 }
  validates :title, uniqueness: true
  validates :image_url, allow_blank: true, format: {
    with: %r{\.(gif|jpg|png)$}i,
    message: 'must be a URL for GIF, JPG or PNG image.'
  }
  
  private
  
  def ensure_not_referenced_by_any_line_item
    if line_items.empty?
      return true
    else
      errors.add :base, 'Line items present'
      return false
    end
  end
end