RSpec - 未初始化的常量，例如 double答案

【问题标题】：RSpec - uninitialized constant for instance doubleRSpec - 未初始化的常量，例如 double
【发布时间】：2017-12-15 21:07:38
【问题描述】：

我使用 TDD 方法使用 RSpec 构建的小型 API 出现名称错误

NameError:
  uninitialized constant ExpenseTracker::API::Ledger

API.rb

require "sinatra/base"
require "json"

module ExpenseTracker
  class API < Sinatra::Base

def initialize(ledger: Ledger.new) # default value so callers can just say API.new and get the default
  @ledger = ledger
  super() # rest of initialization from Sinatra
end

# Later, callers do this ledger: Ledger.new
app = API.new()

post '/expenses' do
  JSON.generate('expense_id' => 42)
end

get '/expenses/:date' do
  JSON.generate([])
end
end
end

api_spec.rb

require_relative "../../../app/api"
require "rack/test"

module ExpenseTracker

RecordResult = Struct.new(:success?, :expense_id, :error_message)

RSpec.describe API do
include Rack::Test::Methods

def app
  API.new(ledger: ledger)
end

let(:ledger) { instance_double('ExpenseTracker::Ledger') }

describe "POST /expense" do
  context "when the expenseis successfully recorded" do
    it 'returns the expense id'do
      allow(ledger).to receive(:record)
      .with(expense)
      .and_return(RecordResult.new(true, 417, nil))

    post '/expense', JSON.generate(expense)

    parsed = JSON.parse(last_response.body)
    expect(parsed).to include('expense_id': 417)
    end
    it 'responds with a 200 (OK)'
  end

  context "when the expense fails validation" do
    it 'returns an error message'
    it 'responds with 422 (Unprocessable entity)'
  end

end
end
end

以下是我得到的错误：

An error occurred while loading ./api_spec.rb.
Failure/Error:
  def initialize(ledger: Ledger.new) # default value so callers can just say API.new and get the default
    @ledger = ledger
    super() # rest of initialization from Sinatra
  end

NameError:
  uninitialized constant ExpenseTracker::API::Ledger

/Users/Denis/Desktop/TDD/Effective_Testing_with_Rspec3/04-acceptance-specs/expense_tracker/app/api.rb:7:in `initialize'
/Users/Denis/Desktop/TDD/Effective_Testing_with_Rspec3/04-acceptance-specs/expense_tracker/app/api.rb:13:in `<class:API>'
/Users/Denis/Desktop/TDD/Effective_Testing_with_Rspec3/04-acceptance-specs/expense_tracker/app/api.rb:5:in `<module:ExpenseTracker>'
/Users/Denis/Desktop/TDD/Effective_Testing_with_Rspec3/04-acceptance-specs/expense_tracker/app/api.rb:4:in `<top (required)>'
./api_spec.rb:1:in `require_relative'
./api_spec.rb:1:in `<top (required)>'

我错过了什么吗？我试图尝试将账本：Ledger.new 传递给 app = API.new，但没有克服这个错误。

任何帮助或想法都会很棒！

【问题讨论】：

标签： api rspec sinatra bdd nameerror

【解决方案1】：

好吧，在桌子上敲了很多头之后，这个问题就解决了。

我不得不注释掉 app = API.new，因为这还没有实现，每次我在规范中加载文件时都会出错。

# Later, callers do this ledger: Ledger.new
app = API.new()

现在继续下一个失败的规范，哈哈！

【讨论】：