Rails Rspec - 如何设置多态 has_many 关联

Question

我有一个模型（支付），它通过多态关联属于另一个模型（事件）。

一些测试失败，因为支付模型在验证中访问了所有者模型（事件），但该事件返回 nil。直接在浏览器中测试应用程序时，所有功能都可以正常工作。 我在下面的payment.rb 中添加了更多的 cmets。

我尝试在工厂中定义关联，但没有成功。

在规范中建立这种关联的最佳方式是什么？

# models/event.rb

class Event < ApplicationRecord

  has_many :payments, as: :payable, dependent: :destroy

end

# models/payment.rb

class Payment < ApplicationRecord

  belongs_to :payable, polymorphic: true

  validate :amount_is_valid

  def amount_is_valid

    if amount.to_i > payable.balance.to_i
      errors.add(:amount, "can't be higher than balance")
    end

  end
  
end

本规范中的两个示例都失败了。

# spec/models/payment_spec.rb

require 'rails_helper'

RSpec.describe Payment, type: :model do
  
  let!(:event) { FactoryBot.create(:event, event_type: 'test', total: 10000, balance: 10000) }
  let!(:user) {FactoryBot.create(:user)}
  let!(:payment) { 
    FactoryBot.build(:payment, 
      amount: 300,
      method: 'cash', 
      payer_id: user.id,
      payable_id: event.id, 
      status: 1,
    )
  }

  describe 'Association' do
    it do 
      
      # This will fail with or without this line 
      payment.payable = event

      is_expected.to belong_to(:payable)
    end

  end

  # Validation
  describe 'Validation' do

    describe '#amount_is_valid' do 
      it 'not charge more than event balance' do 

        # This will make the test pass. The actual spec has a lot more examples though,
        # would rather just set the association once.
        
        # payment.payable = event 

        payment.amount = 5000000
        payment.validate 
        expect(payment.errors[:amount]).to include("can't be higher than balance")
      end
    end
 
  end 
end

输出

# bundle exec rspec spec/models/payment_spec.rb

Randomized with seed 42748

Payment
  Association
    should belong to payable required: true (FAILED - 1)
  Validation
    #amount_is_valid
      not charge more than event balance (FAILED - 2)

Failures:

  1) Payment Association should belong to payable required: true
     Failure/Error: if amount.to_i > payable.balance.to_i
     
     NoMethodError:
       undefined method `balance' for nil:NilClass
     # ./app/models/payment.rb:9:in `amount_is_valid'
     # ./spec/models/payment_spec.rb:23:in `block (3 levels) in <top (required)>'
     # ./spec/rails_helper.rb:80:in `block (3 levels) in <top (required)>'
     # ./spec/rails_helper.rb:79:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:108:in `block (2 levels) in <top (required)>'

  2) Payment Validation #amount_is_valid not charge more than event balance
     Failure/Error: if amount.to_i > payable.balance.to_i
     
     NoMethodError:
       undefined method `balance' for nil:NilClass
     # ./app/models/payment.rb:9:in `amount_is_valid'
     # ./spec/models/payment_spec.rb:39:in `block (4 levels) in <top (required)>'
     # ./spec/rails_helper.rb:80:in `block (3 levels) in <top (required)>'
     # ./spec/rails_helper.rb:79:in `block (2 levels) in <top (required)>'
     # ./spec/spec_helper.rb:108:in `block (2 levels) in <top (required)>'

Top 2 slowest examples (0.29972 seconds, 71.6% of total time):
  Payment Association should belong to payable required: true
    0.28796 seconds ./spec/models/payment_spec.rb:18
  Payment Validation #amount_is_valid not charge more than event balance
    0.01176 seconds ./spec/models/payment_spec.rb:32

Finished in 0.4186 seconds (files took 4.31 seconds to load)
2 examples, 2 failures

Failed examples:

rspec ./spec/models/payment_spec.rb:18 # Payment Association should belong to payable required: true
rspec ./spec/models/payment_spec.rb:32 # Payment Validation #amount_is_valid not charge more than event balance

---

更新

根据 Schwern 的反馈通过规范。 仍然使用金额的自定义验证，因为balance 是关联payable 上的字段，而不是payment（无法找到从内置验证帮助程序内部访问关联模型的方法）

# payment.rb

class Payment < ApplicationRecord

  belongs_to :payable, polymorphic: true

  validates :payable, presence: true 
  validate :amount_is_valid 
  
  def amount_is_valid
    if amount > payable.balance
      errors.add(:amount, "can't be greater than balance")
    end
  end

end

# spec/models/payment_spec.rb

require 'rails_helper'

RSpec.describe Payment, type: :model do
  
  let(:event) { FactoryBot.create(:event, event_type: 'test', total: 10000, balance: 10000) }
  let(:user) {FactoryBot.create(:user)}
  let(:payment) { 
    FactoryBot.build(:payment, 
      amount: 300,
      method: 'cash', 
      payer_id: user.id,
      payable: event, 
      status: 1,
    )
  }

  describe '#payable' do
    it 'is an Event' do
      expect(payment.payable).to be_a(Event)
    end
  end
  
  describe '#amount' do 
    context 'amount is higher than balance' do 
      before {
        payment.amount = payment.payable.balance + 1
      }
      it 'is invalid' do 
        payment.validate
        expect(payment.errors[:amount]).to include("can't be greater than balance")
      end
    end
  end

end

Answer 1

您的第一个测试并没有像您认为的那样失败。它在下一行失败，is_expected.to belong_to(:payable)。

您正在设置payment，但您正在测试implicitly defined subject，它将是Payment.new。

is_expected.to belong_to(:payable)

相当于...

expect(subject).to belong_to(:payable)

因为你没有定义 subject 这是...

expect(Payment.new).to belong_to(:payable)

Payment.new 没有定义payable，因此出现amount_is_valid 验证错误。

要解决此问题，请直接测试 payment。我建议您在学习 RSpec 时远离subject。而且你不应该设置payment.event，它已经在工厂设置了。

describe 'Association' do
  expect(payment).to belong_to(:payable)
end

但我不知道belong_to 匹配器。您不应该直接检查实现，而应该检查它的行为。您想要的行为是让payment.payable 返回Payable。

describe '#payable' do
  it 'is a Payable' do
    expect(payment.payable).to be_a(Payable)
  end
end

---

第二次失败是因为您错误地初始化了您的付款。您传入payable_id: event.id，但未设置payable_type。没有payable_type，它不知道这个ID是什么类。

相反，直接传入对象。

let!(:payment) { 
  FactoryBot.build(:payment, 
    amount: 300,
    method: 'cash', 
    payer: user,
    payable: event, 
    status: 1,
  )
}

---

一些更一般的清理...

• let! 将始终运行该块，无论它是否被使用。除非您特别需要，否则请使用 let，这些块将根据需要运行。
• 您希望payable 存在，因此请验证payable 的存在。
• 在金额上使用内置的numericality validator。

class Payment < ApplicationRecord

  belongs_to :payable, polymorphic: true
  validates :payable, presence: true

  validates :amount, numericality: {
    less_than_or_equal_to: balance,
    message: "must be less than or equal to the balance of #{balance}"
  }
end

require 'rails_helper'

RSpec.describe Payment, type: :model do
  let(:event) {
    create(:event, event_type: 'test', total: 10000, balance: 10000)
  }
  let(:user) { create(:user) }
  let(:payment) {
    build(:payment, 
      amount: 300,
      method: 'cash', 
      payer: user,
      payable: event,
      status: 1
    )
  }

  # It's useful to organize tests by method.
  describe '#payable' do
    it 'is a Payable' do
      expect(payment.payable).to be_a(Payable)
    end
  end

  describe '#amount' do
    # Contexts also help organize and name your tests.
    context 'when the amount is higher than the payable balance' do
      # This code will run before each example.
      before {
        # Rather than hard coding numbers, make your tests relative.
        # If event.balance changes the test will still work.
        payment.amount = payment.payable.balance + 1
      }
    
      it 'is invalid' do 
        expect(payment.valid?).to be false
        expect(payment.errors[:amount]).to include("must be less than or equal to")
      end
    end
  end
end