在尝试模拟Hash Elements的gets和puts时,RSpec无法定义单例错误

Question

我有一个Book Model,它是一个ruby脚本,可以为程序中提到的某些预定义书籍标题分配价格.以下是书籍模型的外观: -

class Book

  attr_accessor :books  
  def initialize books
    puts "Welcome to setting book price program"
    @books = books
  end

  def get_prices
    puts "Please enter appropriate price for each book item:-"
    count = 0
    @books = @books.inject({}) { |hash, book|
      print "#{book.first}: "
      price = STDIN.gets.chomp
      while (price !~ /^[1-9]\d*$/ && price != "second hand")
        puts "Price can't be 0 or a negative integer or in decimal format or alphanumeric. \nPlease input appropriate price in integer"
        price = STDIN.gets.chomp #gets.chomp - throws error
      end
      price == "second hand" ? price = "100" : price #takes a default price
      hash[book.first] = price.to_i
      hash
    }
  end

end

books = {"The Last Samurai" => nil,
         "Ruby Cookbook" =>  nil,
         "Rails Recipes" =>  nil,
         "Agile Development with Rails" =>  nil,
         "Harry Potter and the Deathly Hallows" =>  nil}


book_details = Book.new(books)
book_details.get_prices
puts "\n*******Books Details:#{book_details.books}******\n"

我正在尝试编写一个测试用例,检查每个图书项目的正确价格输入.如果价格输入不当,则应要求用户重新输入价格.该计划做得很好.但是当我尝试使用RSpec模拟这种行为时,我遇到了困难.

require 'spec_helper'

describe Book do

  before :each do
    books = {"The Last Samurai" => nil,
         "Ruby Cookbook" =>  nil,
         "Rails Recipes" =>  nil,
         "Agile Development with Rails" =>  nil,
         "Harry Potter and the Deathly Hallows" =>  nil}
    @book = Book.new(books)
  end

  describe "#new" do
    it "Should be an instance of the Book" do
      @book.should be_an_instance_of Book
    end
  end

  describe "#getprice" do
    it "Should get the price in the correct format or else return appropriate error" do
      puts "\n************************************************************************\n"
      book_obj = @book
      STDOUT.should_receive(:puts).and_return("Welcome to setting book price program")
      book_obj.get_prices.should_not be_nil
      book_obj.books["The Last Samurai"].stub!(:gets) {"40"} #trying to set the value for one book using Hash
      book_obj.books["The Last Samurai"].should == 40 #verifying the value set for a particular key is accurate
    end
  end

end

你甚至可以从Github 克隆这个代码来试试这个.我使用的是Ruby 1.9.3和rspec 2.11.0

The error that I'm getting currently is:-

Failures:

  1) Book#getprice Should get the price in the correct format or else return appropriate error
     Failure/Error: book_obj.books["The Last Samurai"].stub!(:gets) {"40"} #trying to set the value for one book using Hash
     TypeError:
       can't define singleton
     # ./spec/book_spec.rb:31:in `block (3 levels) in <top (required)>'

Finished in 7.61 seconds
2 examples, 1 failure

Failed examples:

rspec ./spec/book_spec.rb:21 # Book#getprice Should get the price in the correct format or else return appropriate error

更新的问题

对于糟糕的用户输入,使用以下测试用例我收到以下错误.我怎样才能正确处理这个？我尝试了几种选择,但它们似乎都失败了.请参阅规范代码段中每个选项的注释.

 it "Incorrect input format should return error message asking user to re input" do
      puts "\n************************************************************************\n"
      book_obj = @book
      STDIN.stub(:gets) { "40abc" }

      #book_obj.get_prices.should be_nil --> adding this line of code goes into an infinite loop with the error message below
      #Price cannot be 0 or a negative integer or in decimal format or alphanumeric. \nPlease input appropriate duration in integer\n

      STDOUT.should_receive(:puts).and_return("Price cannot be 0 or a negative integer or in decimal format or alphanumeric. \nPlease input appropriate duration in integer\n")

      #the below two tests fails with syntax error - don't seem that easy to figure out what's going wrong

      #STDOUT.should_receive("Price cannot be 0 or a negative integer or in decimal format or alphanumeric. \nPlease input appropriate duration in integer\n")
      #STDOUT.should == "Price cannot be 0 or a negative integer or in decimal format or alphanumeric. \nPlease input appropriate duration in integer\n"
    end


Failures:

  1) Book#getprice Incorrect input format should return error message asking user to re input
     Failure/Error: STDOUT.should_receive(:puts).and_return("Price cannot be 0 or a negative integer or in decimal format or alphanumeric. \nPlease input appropriate duration in integer\n")
       (#<IO:0x00000001c7b298>).puts(any args)
           expected: 1 time
           received: 0 times
     # ./spec/book_spec.rb:40:in `block (3 levels) in <top (required)>'

我真的很感激任何指导如何做到这一点.谢谢.

Answer 1

如果您运行带有该--backtrace标志的规范,您将在https://github.com/rspec/rspec-mocks/blob/v2.13.0/lib/rspec/mocks/method_double.rb#L140上看到该错误.,其中rspec-mocks试图获取对象的单例类被存根或模拟.这适用于大多数类的实例,但规范中存在错误.

该代码发送gets到STDIN,但规范试图存根gets上book_obj.books["The Last Samurai"],这是一个int在时间,你不能从拿到单int:

$ irb
1.9.3-p392 :001 > class << 1; self; end
TypeError: can't define singleton
        from (irb):1
    from /Users/david/.rvm/rubies/ruby-1.9.3-p392/bin/irb:16:in `<main>'

如果我理解正确,您想进行两项更改.首先,将脚本的最后几行移动到一个单独的文件中,当您运行规范例如bin/books时它不会被加载(它可能需要book.rb然后添加这些行).

接着,移除短截线线路gets上book_obj.books["The Last Samurai"],并添加一短截线线路gets上STDIN,而不是,之前调用该线get_prices(这是当所述交互瓦特/ STDIN发生):

STDIN.stub(:gets) { "40" }
book_obj.get_prices.should_not be_nil

这至少会让你的规格通过.

在一般情况下,代码,涉及W/STDIN和STDOUT直接是很难在对象级别符合规范,因为测试工具,如RSpec的,MINITEST等,都使用STDOUT提出自己的信息,所以你最终在shell很多混乱的噪音.我建议要么改变设计注入输入/输出流的书类(可STDIN与STDOUT当您运行脚本,但测试双打当你运行RSpec的),或者使用类似的工具阿鲁巴,其设计符合规范交互式shell脚本.