在本文中将利用TDD的思维来探讨email的正则表达式。适用于初学者理解TDD和正则表达式的入门。之所以为利用TDD思维而不直言利用TDD是因为在真实开发实践中的TDD实现细节和本文例子略有不同，不希望被误导。而正则表达是软件开发者的利器，你有什么理由不获得这项技能呢...

In this article we will explore the email Regex with TDD thinking which is good for beginner to understand TDD and learn Regex. The reason of TDD Thinking not TDD in title is there is a little difference between the real project and my demo in implementation details. And Regex as an useful weapon of developer we really has no reason not to get close to it...