测试变量范围关联

Question

我正在努力使我的测试变得健壮且非常可靠，并且我一直在将一些复杂的查询和关联分解为更小的查询和关联，或者重构数据并将其移动到范围中。

给定以下类：

class Item < ActiveRecord::Base
  belongs_to :location

  scope :in_location, ->(location) { where(location: location) }
  scope :findable,    ->(location, not_ids) {
    in_location(location).where.not(id: not_ids)
  }
end

class Container < ActiveRecord::Base
  belongs_to :location
  # THIS IS WHAT I WANT TO TEST 
  has_many :findable_items, ->(container) { 
    findable(container.location, container.not_findable_ids)
  }, class_name: 'Item'
end

您将如何测试像这样的变量 has_many 关系而不会在很大程度上影响数据库？我知道我可以自己测试 Item.findable 方法；我感兴趣的是 container.findable_items 方法。

注意：被测试的实际关联比这更复杂，并且需要相当广泛的设置；它通过其他一些嵌套关联和范围运行。如果可能的话，我想避免这种设置，只是测试使用正确的值调用范围。

我的 Gemfile 的相关部分：

rails (4.2.3)
shoulda-matchers (2.6.2)
factory_girl (4.5.0)
factory_girl_rails (4.5.0)
rspec-core (3.3.2)
rspec-expectations (3.3.1)
rspec-its (1.2.0)
rspec-mocks (3.3.2)
rspec-rails (3.3.3)

我的项目中有 shoulda-matchers，所以我可以进行基本的健全性测试：

it { should have_many(:findable_items).class_name('Item') }

但这失败了：

describe 'findable_line_items' do
  let(:container) { @container } # where container is a valid but unsaved Container
  let(:location)  { @container.location }
  it 'gets items that are in the location and not excluded' do
    container.not_findable_ids = [1,2]
    # so it doesn't hit the database
    expect(Item).to receive(:findable).with(location, container.not_findable_ids) 
    container.findable_items
  end
end

此规范失败并出现以下错误：

1) Container findable_line_items gets items that are in the location and not excluded
 Failure/Error: container.findable_items
 NoMethodError:
   undefined method `except' for nil:NilClass
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/association_scope.rb:158:in `block (2 levels) in add_constraints'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/association_scope.rb:154:in `each'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/association_scope.rb:154:in `block in add_constraints'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/association_scope.rb:141:in `each'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/association_scope.rb:141:in `each_with_index'
 # /[redacted]/activerecord-4.2.3/lib/active_record/associations/association_scope.rb:141:in `add_constraints'
 # /[redacted]/activerecord-4.2.3/lib/active_record/associations/association_scope.rb:39:in `scope'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/association_scope.rb:5:in `scope'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/association.rb:97:in `association_scope'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/association.rb:86:in `scope'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/collection_association.rb:423:in `scope'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/collection_proxy.rb:37:in `initialize'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/relation/delegation.rb:106:in `new'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/relation/delegation.rb:106:in `create'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/collection_association.rb:39:in `reader'
 # /[redacted]/gems/activerecord-4.2.3/lib/active_record/associations/builder/association.rb:115:in `pickable_items'
 # ./spec/models/container_spec.rb:25:in `block (3 levels) in <top (required)>'

在不实际设置满足所有要求的项目的情况下，如何通过此规范？

Answer 1

我最终采用了这样的解决方案：

describe 'findable_line_items' do
  let(:container) { @container } # where container is a valid but unsaved Container
  let(:location)  { @container.location }
  it 'gets items that are in the location and not excluded' do
    # so it doesn't hit the database
    expect(Item).to receive(:findable).with(location, container.not_findable_ids).and_call_original
    expect(container).to receive(:location).and_call_original
    expect(container).to receive(:not_findable_ids).and_call_original
    container.findable_items
  end
end

发生的错误是在 ActiveRecord 关联设置中的某处；它试图在从我的 Item 存根返回的 nil 对象上实例化一个 ActiveRecord 数组。添加.and_call_original 解决了这个错误。

我并不真正关心测试是否从该关联返回了正确的对象，因为该范围正在其他地方进行测试，只是该范围正在被使用。在这种情况下，它仍然会访问数据库，但不是设置完整测试所需的 15 次。