Ruby on rails rspec 销毁计数失败

Question

我已经为简单的应用程序编写了一些测试。我的 authors_controller 中的 #destroy 方法有问题。正如我从一些教程中所做的那样（许多来源显示了类似的方法）我想它应该可以工作，但是发生了这样的错误：

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

这是我的代码：

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

let 调用直到您第一次提到该变量时才进行，因为它是惰性求值。这意味着在您的 expect 块中，您同时创建和销毁了记录，导致整体变化为 0。

在块外创建 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，告诉 let 块不要使用 let! 延迟计算：

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

Ruby on rails rspec 销毁计数失败

Ruby on rails rspec destroy count fails

rspec

ruby-on-rails

destroy