RSpec自定义matcher

链接 https://relishapp.com/rspec/rspec-expectations/v/3-4/docs/custom-matchers/define-a-custom-matcher#define-aliases-for-your-matcher

 require 'rspec/expectations'
 class String
   def words
     split('')
   end
 end

 RSpec::Matchers.define :have_5_words do
   match do |thing|
      thing.words.length == 5
   end
 end

 RSpec.describe String do
   it { expect("hello").to have_5_words }
 end

2.0版本 链接 https://relishapp.com/rspec/rspec-expectations/v/2-0/docs/matchers/have-n-items-matcher

 class String
   def words
     split(' ')
   end
 end

  describe String.new('hello') do
       it {
         should have(5).words }
     end