What is Behaviour-Driven Development (BDD)?


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Praise Iwuh

January 23, 2023

What is Behaviour-Driven Development (BDD)?

Behaviour-Driven Development

Behaviour-driven development (BDD) is an Agile software development methodology that designs applications based on business requirements. It focuses on the application's overall behaviour, which the end user expects to encounter during use. BDD is derived from Test-driven development, where the testing is conducted before writing production code. In BDD, however, the application's expected behaviour is mapped out first, and the code is written to represent those behaviours.


One defining feature of BDD is that the code is written in plain English text rather than in complex programming languages. This aims to make it easier for non-technical team members and stakeholders to understand feedback and give more input.

Behaviour-driven development helps development teams avoid bulky code and unnecessary features while promoting a focus on a specific outcome and absolute parity between technical and non-technical teams, business professionals and engineers. This methodology is an extension of TDD, sharing most of its features, principles and advantages. Where TDD seeks to build the product accurately, BDD aims to build the accurate product.


How BDD works

A BDD life cycle typically begins with a conversation between the developers, product owners, and customers to create a picture of how the product should function. These desired behaviours are then laid out as objectives for the developers. Test cases are written out of the requirements, and if the product passes the behaviour tests, it is deemed ready for conveyance to the client. Behaviour-driven development revolves around conducting behaviour-specific tests or functional specifications that outline executable scenarios for the application.

Testing is represented with a "Given-When-Then" formula construct. This formula defines behaviour in the following ways:

  • Given defines the preconditions for a particular behaviour.
  • When defines when a specific application event may occur.
  • Then defines the test outcome whenever preconditions and matched events are matched.

BDD functions by employing a set of practices that focus on creating behavior-specific tests and executable scenarios for applications. The process involves:

Utilizing the 5 Whys Principle and If-Then Scenarios

BDD starts by applying the 5 Whys principle and if-then scenarios to generate user stories. This helps establish the relationship between application features and their business purposes.

Defining a Singular Outcome for Each Behavior

Every behavior is identified with a single, well-defined outcome. This ensures that the expectations from each aspect of the application are clear and unambiguous.

Translation into Domain-Specific Language (DSL)

Each scenario is translated into Domain-Specific Language (DSL) to enhance accurate communication. This step ensures that all stakeholders, including domain experts, testers, and developers, can easily understand the specified behaviors.

Documentation Consolidation

All identified behaviors are gathered into a comprehensive set of documentation. This documentation is accessible to all team members, including developers, testers, and stakeholders, facilitating a shared understanding of the expected application behavior.


Stages of BDD

BDD framework involves three main stages: discovery, formulation, and automation.


This is the first phase of the behaviour-driven development framework, where the acceptance criteria are researched and decided.

The acceptance criteria are based on product type, key features, target audience, present market, and other factors. This behaviour-driven development requires the collaborative input of all team members to come up with the acceptance criteria.


The formulation phase is mainly relevant when a backlog item is just about to get implemented. The basic purpose of this phase is to ensure that the acceptance criteria are confirmed and ready to be applied in real time. Acceptance tests in the formulation phase execute this part.

The purpose of acceptance testing is to run quality assurance methods to determine whether an application or product is as per the requirements. It decides to what extent or degree you can accept a product based on end-user needs and approval. As such, the formulation phase is dedicated to turning the initial acceptance criteria into a stable version with less ambiguity or flaws.


The Automation phase automates the process of acceptance tests. Here, acceptance tests are automated and then run to determine if the new behaviours are compatible with the system.


Examples of Behaviour Driven Development frameworks

To rightly implement BDD framework, one must be familiar with the BDD tools. Below, we discuss three top BDD tools: Cucumber, Gauge and JBehave.


Cucumber: Cucumber is an open-source testing BDD framework that enables developers to write requirements in Gherkin. This language allows anyone to read and understand the information easily. It supports several programming languages, including Ruby, Java and .NET, and software platforms like Ruby on Rails, Selenium and Spring Framework.

Gauge: Gauge is a cross-browser, open-source test automation framework. It works with multiple programming languages and integrates with several integrated development environments and continuous integration servers, including IntelliJ and Jenkins.

JBehave: This is an open-source BDD framework designed for microservices testing and Java-based development. While JBehave is restricted to Java implementations, it offers many customisation options for developers to configure their BDD tests.

Advantages of Behavior-Driven Development

Improved Collaboration and Communication

BDD promotes collaboration among diverse teams, ensuring a shared understanding of desired behaviors. The use of a common language reduces communication gaps between technical and non-technical team members.

User-Centric Development

BDD emphasizes understanding and defining behavior from the user's perspective, aligning development with user expectations.

Living Documentation

BDD scenarios serve as living documentation, automatically updated as the codebase evolves.

Early Issue Detection

Automated tests in BDD are created early, facilitating early detection and resolution of issues.

Focus on Business Value

BDD prioritizes development efforts based on business value, ensuring alignment with critical requirements.

Incremental Development

BDD supports incremental and iterative development, allowing for quick adaptation to changing requirements.

Disadvantages of Behavior-Driven Development

Learning Curve

Implementing BDD may require time for teams to adapt to new tools and practices.

Initial Overhead

There is an initial time and effort overhead in creating comprehensive scenarios and setting up BDD infrastructure.

Overemphasis on Testing

BDD may lead to an overemphasis on testing, potentially neglecting other critical development activities.

Misuse of Language

The use of natural language can lead to ambiguity if not carefully crafted, necessitating clear communication.

Dependency on Tools

BDD relies on specific tools, and challenges may arise if these tools are not well-maintained or face compatibility issues.

Maintenance Challenges

Keeping scenarios accurate and up-to-date as the application evolves can pose challenges and requires careful attention.

Differences Between BDD and TDD

  • The TDD approach helps make an application stable, but understanding automated tests is challenging for non-technical team members. The primary aim of BDD framework was to address this.
  • TDD focuses on developing unit tests by developers, while BDD focuses on specifying product behaviour in a human-friendly language.
  • The BDD approach gives clarity as the front end is written in plain English. It can then be reviewed easily by anyone in the team without requiring technical knowledge.


Behaviour-driven development closes the gap between developers and businesses by making implementation as close to the behaviour as possible. It enforces good structure and layers for automation. In a nutshell, BDD is unique because it can be easily understood by non-technical individuals and focuses on collaborating with business organisations.

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