这是一篇翻译稿，方便给不知道BDD的同学扫盲。原文链接：What is BDD (Behavior Driven Development)? | Agile Alliance

Definition定义

Behaviour Driven Development (BDD) is a synthesis and refinement of practices stemming from Test Driven Development (TDD) and Acceptance Test Driven Development (ATDD). BDD augments TDD and ATDD with the following tactics:

行为驱动开发 (BDD) 是对源自测试驱动开发 (TDD) 和验收测试驱动开发 (ATDD) 的实践的整合和改进。 BDD 通过以下策略增强 TDD 和 ATDD：

• Apply the “Five Why’s” principle to each proposed user story, so that its purpose is clearly related to business outcomes
• thinking “from the outside in”, in other words implement only those behaviors which contribute most directly to these business outcomes, so as to minimize waste
• describe behaviors in a single notation which is directly accessible to domain experts, testers and developers, so as to improve communication
• apply these techniques all the way down to the lowest levels of abstraction of the software, paying particular attention to the distribution of behavior, so that evolution remains cheap
• 将“五个为什么”原则应用于每个提议的用户故事，使其目的与业务成果明确相关
• “由外而内”思考，换言之，只实施对这些业务成果有最直接贡献的行为，以最大程度地减少浪费
• 用单一符号描述行为，领域专家、测试人员和开发人员可以直接访问，以改善沟通
• 将这些技术一直应用到软件的最低抽象级别，特别注意行为的分布，从而用较低的成本实现功能的演进

Also Known As别称

BDD is also referred to as Specification by Example.

BDD 也称为用例子来描述的需求规格说明书。

Expected Benefits可能带来的好处

Teams already using TDD or ATDD may want to consider BDD for several reasons:

已经使用 TDD 或 ATDD 的团队可能出于以下几个原因想要考虑 BDD：

• BDD offers more precise guidance on organizing the conversation between developers, testers and domain experts
• notations originating in the BDD approach, in particular the given-when-then canvas, are closer to everyday language and have a shallower learning curve compared to those of tools such as Fit/FitNesse
• tools targeting a BDD approach generally afford the automatic generation of technical and end user documentation from BDD “specifications”
• BDD 为组织开发人员、测试人员和领域专家之间的对话提供了更精确的指导
• 与 Fit/FitNesse 等工具相比，源自 BDD 方法的符号，尤其是场景-时间-动作画布，更接近日常语言，并且学习曲线更浅
• 针对 BDD 方法的工具通常能够根据 BDD“规范”自动生成技术和最终用户文档

Common Pitfalls弊端

Although Dan North, who first formulated the BDD approach, claims that it was designed to address recurring issues in the teaching of TDD, it is clear that BDD requires familiarity with a greater range of concepts than TDD does, and it seems difficult to recommend a novice programmer should first learn BDD without prior exposure to TDD concepts

尽管首先制定 BDD 方法的 Dan North 声称它旨在解决 TDD 教学中反复出现的问题，但很明显，BDD 需要比 TDD 熟悉更多的概念，而且也不推荐一个新手程序员在没有任何TDD概念基础的情况下接触 BDD。

The use of BDD requires no particular tools or programming languages, and is primarily a conceptual approach; to make it a purely technical practice or one that hinges on specific tooling would be to miss the point altogether

BDD 的使用不需要特定的工具或编程语言，主要是一种概念方法； 这容易使其容易成为纯粹的技术实践，如果没有好的工具，相关理念很难实施。

Origins缘起

• 2003: agiledox, the ancestor of BDD, is a tool generating technical documentation automatically from JUnit tests, written by Chris Stevenson
• 2004: Chris Matts and Dan North proposed the given-when-then canvas to expand the scope of BDD to business analysis and documents
• 2004: in order to test his hypotheses about de-emphasizing “test” terminology in favor of “behavior”, Dan North releases JBehave
• 2006: Dan North documents the approach in  “Introducing BDD”
• 2006-2009: several new tools are released confirming the community’s investment in BDD, such as RSpec or more recently, Cucumber and GivWenZen

Signs of Use使用说明

• A team using BDD should be able to provide a significant portion of “functional documentation” in the form of User Stories augmented with executable scenarios or examples.
• Instead of referring to “tests”, a BDD practitioner will prefer the terms “scenario” and “specification”. As currently practiced, BDD aims to gather in a single place the specification of an outcome valuable to a user, generally using the role-feature matrix of (User Stories), as well as examples or scenarios expressed in the form given-when-then; these two notations being often considered the most readable.
• In emphasizing the term “specification”, the intent of BDD is to provide a single answer to what many Agile teams view as separate activities: the creation of unit tests and “technical” code on one hand, the creation of functional tests and “features” on the other hand. This should lead to increased collaboration between developers, test specialists, and domain experts.
• Rather than refer to “the unit tests of a class”, a practitioner or a team using BDD prefers to speak of “the specifications of the behavior of the class”. This reflects a greater focus on the documentary role of such specifications: their names are expected to be more expressive, and, when completed with their description in given-when-then format, to serve as technical documentation.
• Rather than refer to “functional tests”, the preferred term will be “specifications of the product’s behavior”. The technical aspects of BDD are placed on an equal footing with techniques encouraging more effective conversation with customers, users and domain experts.
• In addition to refactoring techniques already present in TDD, the design philosophy in BDD pays particular attention to appropriate distribution of responsibilities among classes, which leads its practitioners to emphasize “mocking”.
• 使用 BDD 的团队应该能够以用户故事的形式提供大部分“功能文档”，并增加了可执行场景或示例。
• BDD 从业者不会提及“测试”，而是更喜欢“场景”和“规范”这两个术语。按照目前的做法，BDD 的目标是在一个地方收集对用户有价值的结果的规范，通常使用（用户故事）的角色特征矩阵，以及以“场景-时间-行为”形式表达的示例或场景;这两种符号通常被认为是最易读的。
• 在强调术语“规范”时，BDD 的目的是为许多敏捷团队视为独立活动的内容提供单一答案：一方面创建单元测试和“技术”代码，一方面创建功能测试和“特性”。 “ 另一方面。这应该会导致开发人员、测试专家和领域专家之间加强协作。
• 与“类的单元测试”不同，使用 BDD 的从业者或团队更喜欢谈论“类的行为规范”。这反映了对此类规范的文档作用的更大关注：它们的名称应该更具表现力，并且在以“何时给定”格式完成描述后，可用作技术文档。
• 首选术语不是“功能测试”，而是“产品行为规范”。BDD 的技术方面与鼓励与客户、用户和领域专家进行更有效对话的技术处于同等地位。
• 除了 TDD 中已经存在的重构技术，BDD 中的设计理念特别关注类之间的适当职责分配，这导致其从业者强调“mocking”。

Further Reading参考文献

“Introducing BDD”, by Dan North (2006)

“Translating TDD to BDD”, by Liz Keogh (2009)

A tool stack for implementing Behaviour-Driven Development in Python Language by Tavares, Rezende, dos Santos, Manhaes, de Carvalho (2010)