Ruby on rails rspec銷燬計數失敗

Question

我已經爲簡單的應用程序編寫了一些測試。我在我的authors_controller中遇到了#destroy方法的問題。正如我已經這樣做了一些教程（許多來源顯示類似的方法），我想它應該工作，但是發生這樣的錯誤：

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

這裏是我的代碼：

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

直到第一次提到變量時纔會調用let，因爲這是懶惰的評估。這意味着你的expect塊內，你都創建和銷燬記錄，導致0

產生總體變化創造塊的author外：

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 

或者告訴let不要通過使用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