如何在 Active Storage 测试中存根文件大小？ （测试::单元）

Question

我在 personal project 中使用 Active Storage。我想检查是否正在验证文件的最大大小。我不想使用真实文件，但我不知道如何存根对象。

这是测试代码：

test "should not upload file bigger than max size allowed" do
  refute @page.file.attached?

  patch "/#{@page.url}", params: {
    page: {
      url: "/#{@page.url}",
      file: my_stub_file_with_big_size
    }
  }
  assert_response :not_acceptable
  @page.reload

  refute  @page.file.attached?
end

这是对模型的验证：

def file_size
  if file.attached? && file.byte_size > MAX_FILE_SIZE
    file.purge
    errors.add(:file, "File is too big. Max size is 20mb.")
  end
end

Answer 1

我从您的项目中阅读了代码，发现您提出了一个有趣的解决方案，但这里有另一个符合您要求的解决方案。

第 1 步 - 添加摩卡咖啡

Mocha 是 MiniTest 粉丝事实上的存根库，所以像这样将它添加到您的 Gemfile 中。

group :test do
  gem 'mocha'
end

然后运行bundle install 并在您的测试助手中要求 mocha，如下所示：

# test/test_helper.rb

ENV['RAILS_ENV'] ||= 'test'

require_relative '../config/environment'
require 'rails/test_help'

# add this line
require 'mocha/minitest'

class ActiveSupport::TestCase    
  # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
  fixtures :all    
end

第 2 步 - 创建一个虚拟测试文件

在test/fixtures/files/ 中放置一个名为“test.png”的小文件。请注意，我的文件大小约为 20KB，非常小。

第 3 步 - 添加单元测试

将以下内容添加到test/models/page_test.rb：

test 'file has max size' do
  # get the path of the file
  fixture_path = File.join(Rails.root, 'test', 'fixtures', 'files', 'test.png')

  # open the file  
  fixture_file = File.open(fixture_path)

  # stub the file size to 21 MB
  fixture_file.stubs(:size).returns(21.megabytes)

  # attach the file to your @page instance
  @page.file.attach(io: fixture_file, filename: 'test.png')

  # the record should now be invalid
  refute @page.valid?

  # it should not have an attachment
  refute @page.file.attached?

  # assert the error message matches a regex 
  assert_match /is too big/, @page.errors[:file].to_s
end

第 4 步 - 在最大文件大小边界内测试

让我们通过将以下内容添加到test/models/page_test.rb 来确保可以接受 20MB 的文件：

test 'file with valid size' do
  # get the path of the file
  fixture_path = File.join(Rails.root, 'test', 'fixtures', 'files', 'test.png')

  # open the file  
  fixture_file = File.open(fixture_path)

  # stub the file size to 20 MB
  fixture_file.stubs(:size).returns(20.megabytes)

  # attach the file to your @page instance
  @page.file.attach(io: fixture_file, filename: 'test.png')

  # the record should now be valid
  assert @page.valid?

  # it should have an attachment
  assert @page.file.attached?

  # probably unnecessary, but let's test that there are no errors on @page
  assert_empty @page.errors[:file]
end

第 5 步 - 为快乐路径添加控制器测试

让我们为快乐路径添加一个控制器测试：

test 'should update page' do
  # fixture_file_upload knows where the fixtures folder is
  # and makes sure we have a correctly signed file
  fixture_file = fixture_file_upload('files/test.png', 'image/png')

  # we need to stub the byte_size of any instance of ActiveStorage::Blob
  # as that is what our validations are going to be run against 
  ActiveStorage::Blob.any_instance.stubs(:byte_size).returns(20.megabytes)

  # make sure our ActiveStorage records are created
  assert_difference ['ActiveStorage::Blob.count', 'ActiveStorage::Attachment.count'] do
    # add our fixture file into the params
    patch page_url, params: { page: { file: fixture_file } }
  end

  # make sure we are redirected to the right place 
  assert_redirected_to page_url
end

第 6 步 - 为悲伤路径添加控制器测试

测试上传失败的时间：

test 'should render edit template when update fails' do
  # like before, we get correctly formatted test file by calling
  # fixture_file_upload method and passing in the test file
  fixture_file = fixture_file_upload('files/test.png', 'image/png')

  # stub the byte_size to be 21MB
  ActiveStorage::Blob.any_instance.stubs(:byte_size).returns(21.megabytes)

  # make sure zero ActiveStorage records are created
  assert_no_difference ['ActiveStorage::Blob.count', 'ActiveStorage::Attachment.count'] do
    # send the request
    patch page_url, params: { page: { file: fixture_file } }
  end

  # check the response body for an error message
  assert_match /is too big/, response.body.to_s
end

就是这样。希望对您有所帮助。

Answer 2

我更喜欢在单独的类中处理给定模型上的任何自定义验证，因此我的方法可能不适合您。有关详细信息，请参阅 Rails 文档here。

在我的自定义验证类测试中，我使用 Rspec 的 receive_message_chain 来存根对 ActiveStorage 映像的任何调用。对于有问题的模型，我有一个定义了with_image 特征的工厂（感谢this related answer），然后我对模型的image 进行了必要的调用。不幸的是，这需要您的测试套件中至少有一个图像夹具，但它可以是您想要的任何大小。完整示例如下：

user.rb (model) - 注意自定义 target 选项的使用

class User < ApplicationRecord
  has_one_attached :image

  validates_with ImageValidator, target: :image
end

user.rb（工厂）

FactoryBot.define do
  factory :user do
    trait :with_image do
      after(:build) do |user|
        user.image.attach(io: File.open(Rails.root.join('spec', 'fixtures', 'user-image.png')), filename: 'user-image.png', content_type: 'image/png')
      end
    end
  end
end

image_validator.rb（验证类）- 然后使用自定义 target 选项来确定应使用该类验证给定模型上的哪个属性。

class ImageValidator < ActiveModel::Validator
  def validate(record)
    if options[:target].present? && record.send(target).attached?
      if record.send(target).blob.byte_size > 1000000
        record.send(target).purge
        record.errors.add(:image, "Image too large")
      elsif !record.send(target).blob.content_type.starts_with?('image/')
        record.send(target).purge
        record.errors.add(:image, "Incorrect image format")
      end
    end
  end

  private 

  def target
    options[:target].to_s
  end
end

image_validator_spec.rb（测试）

require "rails_helper"

describe ImageValidator do
  subject { build(:user, :with_image) }

  context "when an Image is too large" do
    before do
      allow(subject.image).
        to receive_message_chain(:blob, :byte_size).and_return(1000001)
    end

    it "should be invalid" do
      expect(subject).to be_invalid
    end
  end
end