Ruby on Rails RSpec銷毀計數失敗

Question

我已經為簡單的應用程序編寫了一些測試。 我的authors_controller中的#destroy方法遇到問題。 當我從一些教程中完成此操作時（許多資源都顯示了類似的方法），我想它應該可以工作，但是會發生這種錯誤：

Failure/Error: expect { delete :destroy, id: author.id }.to change(Author, :count).by(-1) expected #count to have changed by -1, but was changed by 0

這是我的代碼：

author_controller_spec.rb

require 'rails_helper'                        

describe AuthorsController do                 
  let(:author) { FactoryGirl.create(:author) }

  describe 'DELETE #destroy' do                                                                            
    it 'deletes author' do                                                      
      expect { delete :destroy, id: author.id }.to change(Author, :count).by(-1)
    end                                                                         
  end                                                                           
end                                                                             

authors_controller.rb

class AuthorsController < ApplicationController
def show
@author = Author.find(params[:id])
end

def new
  @author = Author.new
end

def create
  @author = Author.new(author_params)
  if @author.save
    redirect_to @author
  else
    render 'new'
  end
end

def edit
  @author = Author.find(params[:id])
end

def update
  @author = Author.find(params[:id])

  if @author.update(author_params)
    redirect_to @author
  else
    render 'edit'
  end
end

def destroy
  @author = Author.find(params[:id])
  @author.books.each do |book|
  book.destroy if book.authors.count == 1
  end
  @author.destroy
  redirect_to authors_path
end

def index
  @author = Author.all
end

private

  def author_params
    params.require(:author).permit(:name, :surname, book_ids: [])
  end
end

Answer 1

在您第一次提到該變量之前，不會進行let調用，因為它是惰性計算。 這意味着在您的expect塊中，您同時在創建和銷毀記錄，導致總體變化為0。

在代碼塊之外創建author ：

describe AuthorsController do                 
  let(:author) { FactoryGirl.create(:author) }

  describe 'DELETE #destroy' do   
    author                                                                         
    it 'deletes author' do                                                      
      expect { delete :destroy, id: author.id }.to change(Author, :count).by(-1)
    end                                                                         
  end                                                                           
end 

或者，通過使用let!告訴let塊不要懶惰地求值let! ：

describe AuthorsController do                 
  let!(:author) { FactoryGirl.create(:author) }

  describe 'DELETE #destroy' do                                                                            
    it 'deletes author' do                                                      
      expect { delete :destroy, id: author.id }.to change(Author, :count).by(-1)
    end                                                                         
  end                                                                           
end