[每周软件]：Cucumber：Hello World

##简介##

OSChina 的链接 Cucumber

ruby 的 BDD框架，类似自然语言的DSL，适用于BDD模式和验收测试。

Book

The Rspec Book

The Cucumber Book

##Before Start##

安装，Ruby和RubyGems环境就不说了，那就剩下一句话

<!-- lang: ruby -->
gem install cucumber

##Step By Step ##

1: 描述行为

文件 "./features/greeter_says_hello.feature"

<!-- lang: ruby -->
Feature: greeter says hello
   Cucumber的Hello World

  Scenario: 对世界打个招呼吧
    Given 如果我给了你一个测试的hello
    When 当我执行greet的时候
    Then 我应该看到 "Hello Cucumber!"

一个Feature 可以理解为一个功能，一个Feature由三部分组成：

• 标题：greeter says hello
• 描述：2～4行
• Scenario（场景）： 最后一部分

一个Feature可以有多个场景，标题和描述部分可以使用中文。 一个Scenario是对feature的划分，比如一个登录的feature，scenario可以是不同角色的登录情况。（细节待补） Given When Then 是这种DSL里的关键字 还有And

然后在.目录里运行一下

<!-- lang: ruby -->
 $ cucumber features
        Feature: greeter says hello
          Cucumber的Hello World
        
          Scenario: 对世界打个招呼吧             # features/greeter_says_hello.feature:3
            Given 如果我给了你一个测试的hello       # features/greeter_says_hello.feature:4
            When 当我执行greet的时候        # features/greeter_says_hello.feature:5
            Then 我应该看到 "Hello Cucumber!" # features/greeter_says_hello.feature:6
        
        1 scenario (1 undefined)
        3 steps (3 undefined)
        0m0.003s
        
        You can implement step definitions for undefined steps with these snippets:
        
        Given /^如该我给了你一个测试的hello$/ do
          pending # express the regexp above with the code you wish you had
        end
        
        When /^当我给你一个greet的时候$/ do
          pending # express the regexp above with the code you wish you had
        end
        
        Then /^我应该看到 "(.*?)"$/ do |arg1|
          pending # express the regexp above with the code you wish you had
        end

2: Write a step definition in Ruby

文件：./features/step_definitions/greeter_steps.rb

(注：这里文件名没有硬性规定 是根据内部的代码来查找的，greeter可以用greeter_says_hello_steps.rb)

把上面输出的内容copy进来

<!-- lang: ruby -->
# -*- encoding : utf-8 -*-
    Given /^如该我给了你一个测试的hello$/ do
      pending # express the regexp above with the code you wish you had
    end
    
    When /^当我给你一个greet的时候$/ do
      pending # express the regexp above with the code you wish you had
    end
    
    Then /^我应该看到 "(.*?)"$/ do |arg1|
      pending # express the regexp above with the code you wish you had
    end

运行一下看看结果

<!-- lang: ruby -->
$ cucumber features
    Feature: greeter says hello
      Cucumber的Hello World
    
      Scenario: 对世界打个招呼吧             # features/greeter_says_hello.feature:3
        Given 如该我给了你一个测试的hello       # features/step_definitions/g_steps.rb:2
          TODO (Cucumber::Pending)
          ./features/step_definitions/g_steps.rb:3:in `/^如该我给了你一个测试的hello$/'
          features/greeter_says_hello.feature:4:in `Given 如该我给了你一个测试的hello'
        When 当我给你一个greet的时候        # features/step_definitions/g_steps.rb:6
        Then 我应该看到 "Hello Cucumber!" # features/step_definitions/g_steps.rb:10
    
    1 scenario (1 pending)
    3 steps (2 skipped, 1 pending)
    0m0.004s

pending指正在进行中，因为Given是正在pending，所以跳过了when和then

OK，然后写一些真正的Step

文件：./features/step_definitions/greeter_steps.rb

<!-- lang: ruby -->
# -*- encoding : utf-8 -*-
Given /^如该我给了你一个测试的hello$/ do
  @hello = Hello.new
end

When /^当我给你一个greet的时候$/ do
  @message = @hello.greet
end

Then /^我应该看到 "(.*?)"$/ do |greeting|
  @message.should == greeting
end

这里需要注意的是then里面的 greeting代表的是前面那个描述里面的双引号扩起来的结果

3: Run and watch it fail

<!-- lang: ruby -->
 $ cucumber features
    Feature: greeter says hello
      Cucumber的Hello World
    
      Scenario: 对世界打个招呼吧             # features/greeter_says_hello.feature:3
        Given 如该我给了你一个测试的hello       # features/step_definitions/g_steps.rb:7
          uninitialized constant Hello (NameError)
          ./features/step_definitions/g_steps.rb:8:in `/^如该我给了你一个测试的hello$/'
          features/greeter_says_hello.feature:4:in `Given 如该我给了你一个测试的hello'
        When 当我给你一个greet的时候          # features/step_definitions/g_steps.rb:11
        Then 我应该看到 "Hello Cucumber!" # features/step_definitions/g_steps.rb:15
    
    Failing Scenarios:
    cucumber features/greeter_says_hello.feature:3 # Scenario: 对世界打个招呼吧
    
    1 scenario (1 failed)
    3 steps (1 failed, 2 skipped)
    0m0.003s

4: Write code to make the step pass

文件：./features/step_definitions/greeter_steps.rb

(注：为了简单起见我就直接写到这里面了)

<!-- lang: ruby -->
# -*- encoding : utf-8 -*-
class Hello
  def greet
    "Hello Cucumber!"
  end
end
Given /^如该我给了你一个测试的hello$/ do
  @hello = Hello.new
end

When /^当我给你一个greet的时候$/ do
  @message = @hello.greet
end

Then /^我应该看到 "(.*?)"$/ do |greeting|
  @message.should == greeting
end

5: Run again and see the step pass

<!-- lang: ruby -->
 $ cucumber features
    Feature: greeter says hello
      Cucumber的Hello World
    
      Scenario: 对世界打个招呼吧             # features/greeter_says_hello.feature:3
        Given 如该我给了你一个测试的hello       # features/step_definitions/g_steps.rb:7
        When 当我给你一个greet的时候          # features/step_definitions/g_steps.rb:11
        Then 我应该看到 "Hello Cucumber!" # features/step_definitions/g_steps.rb:15
    
    1 scenario (1 passed)
    3 steps (3 passed)
    0m0.003s

6: Repeat 2-5 until green like a cuke

##Summary##

从Hello World可以看出，cucumber还是很强大滴，并且输出和定义对非专业人员（需求啊 Boss啊 客户啊）都很友好，如果是个不爱写文档的程序员，可以考虑用cucumber来代替一下。

BTW：虽然例子是ruby，不过cucumber还支持其他语言的，这就得看自己了。