I’ve used behavior-driven development in various projects and witnessed the results it can deliver. In this lesson, you’ll discover how BDD functions and why it’s essential for building user-focused software. So, let’s dive into this interesting methodology!
Understanding Behavior-Driven Development (BDD)
Behavior-Driven Development (BDD) is a software development methodology designed to help teams create a shared understanding of what an application should do. I’ve used BDD in various projects throughout my career, and it’s one of the most effective methodologies for ensuring development efforts align with business objectives.
BDD traces back to 2003 when Chris Stevenson created agiledox, a tool for generating technical documentation from JUnit tests. This was the earliest form of what we now call BDD. As developers and business stakeholders began interacting more frequently, software evolution also started to focus on more effectively ensuring software met user needs.
Core principles of BDD include:
- Emphasis on behavior (what the application does) over implementation details (how the application does it)
- Strong collaboration among developers, testers and business stakeholders
- Using natural language to describe what the application should do
- Automated tests, driven by behavior descriptions
BDD differs from many other development processes because it:
- Starts with defining behavior before writing any code
- Emphasizes cross-functional collaboration
- Uses a simple language that everyone understands
- Directly ties requirements to tests and code
Implementing BDD in software teams offers several high-level benefits. First, you’ll notice people communicate more effectively. You’ll also encounter fewer misunderstandings about what the application should do. Finally, BDD leads to a faster feedback loop, which ultimately enables you to ensure the software you build is exactly what the user needs.
Dan North, one of the key thought leaders in the development of BDD, refers to BDD as a “second-generation, outside-in, pull-based, multiple-stakeholder, multiple-scale, high-automation, agile methodology.” This lengthy description emphasizes that BDD is all about collaboration, stakeholder involvement and automation in the development process.
The BDD Process and Workflow
BDD involves three steps:
- discovery
- formulation
- automation
The process is powerful because all team members are aligned through each step.
Discovery is a series of collaborative sessions where stakeholders discuss and explore what they want the software to do. This step is essential because it helps you uncover any assumptions and get clarity on the requirements. In other words, these discussions will often bring up important details that you might have missed in a traditional requirements-gathering process.
Formulation is when you transform the discussed behaviors into structured scenarios. These scenarios all follow a specific format – the Given-When-Then format, which I’ll cover more later. This step ensures everyone has a shared understanding of the software’s expected behavior.
Automation is the last step, where developers write code to make the software do what you formulated and create automated tests to ensure the software continues to do what you formulated.
Using BDD within agile is effective because both methodologies value collaboration, iterative development, and continuous feedback. BDD also pairs nicely with agile, as it’s a structured way to capture and verify requirements.
BDD Frameworks and Tools
I’ve used several different BDD frameworks and tools over the years. Each has its own strengths, so the best choice depends on the specific project you’re working on and your team’s preferences.
Popular BDD frameworks include:
- Cucumber: Supports several programming languages
- SpecFlow: .NET development
- Behat: PHP projects
- JBehave: Java-based BDD framework
When choosing a BDD framework for your project, consider the programming languages it supports, how it integrates with your existing development environment, the learning curve for your team, and the available community support and documentation.
Most BDD tools also play nicely with modern development environments. They often have good integrations with version control systems, continuous integration platforms, and other development tools you likely already use.
It’s also worth mentioning that in 2004, Chris Matts and Dan North introduced the given-when-then canvas for business analysis and documents, which is now a central concept in BDD and used by most BDD frameworks.
Writing Effective BDD Scenarios
BDD scenarios are written in the Given-When-Then format, which is a structured way to describe the expected behavior of a particular feature. Here’s what each section means:
- Given: The initial state or context
- When: An action or event
- Then: The expected outcome or behavior
When writing BDD scenarios, remember these best practices:
- Keep the language clear and straightforward.
- Only describe one behavior in each scenario.
- Don’t include any technical details about the scenario in the description.
- Make sure to add any necessary context to the “Given” step.
Common pitfalls to avoid:
- Making scenarios too complex
- Describing implementation details
- Forgetting edge cases or error scenarios
- Using vague, ambiguous language
High-quality BDD scenarios act as living documentation for the project, giving everyone a clearer understanding of the system’s behavior, even if they don’t have much knowledge of software development. As a result, they are particularly useful in CI/CD (continuous integration and continuous delivery) environments.
Implementing BDD in Your Development Process
Introducing BDD to your team takes some strategy and planning. In my experience, I’ve found that introducing BDD to your team is best done gradually.
How to introduce BDD:
- Educate your team about BDD principles and its advantages.
- Start with a small pilot project or even a single feature.
- Get everyone involved in the BDD process.
- Iterate based on feedback and results.
It’s easy to incorporate BDD with existing methodologies like Scrum or Kanban. BDD activities naturally fit within the cadence of agile iterations/sprints.
The most common BDD adoption challenges are:
- Resistance to change from team members
- Initial slowdown in development speed
- Difficulty in writing effective scenarios
To gauge the success of your BDD implementation, consider:
- Fewer defects and less rework
- Better alignment of what you build with what was in the requirements
- Happier stakeholders
- Faster time to market with new features
Day to day, BDD is a repeating cycle of Discovery, Formulation, and Automation. This cyclical nature ultimately ensures continuous improvement and alignment throughout the development process.
BDD vs. Test-Driven Development (TDD)
While BDD and TDD are similar, they also have key differences and unique use cases. I’ve practiced both and can speak to their individual benefits.
The core differences are that:
- BDD focuses on behavior and user stories, while TDD focuses on code design and implementation.
- BDD is typically higher level, while TDD is lower level.
- BDD uses natural language specifications, while TDD uses code level assertions.
You might opt for BDD when:
- You want to improve communication between non-technical and technical team members.
- You want to ensure that your software directly supports business objectives.
- You’re working on a user facing feature.
TDD is likely a better choice when:
- You’re building a complicated algorithm or data structure.
- You want to guarantee code accuracy at a very granular level.
- You’re building an internal system that’s less directly related to a specific user feature.
In many cases, combining BDD and TDD is the best solution. Then, just use BDD for defining high level behavior and TDD to define the low level code. This provides full test coverage and ensures that the software both meets user requirements and has a design conforming to TDD practices.
Transitioning from TDD to BDD requires that you:
- Change the focus from writing code level tests to behavior level tests.
- Involve more team members in the development process.
- Learn how to write effective BDD tests.
That said, it’s worth noting that BDD requires that you understand a broader set of concepts than TDD, making it less suitable for beginners who don’t have previous exposure to these concepts from TDD.
BDD Best Practices and Tips
Effective communication: Communication is essential to successful BDD implementation. Regular meetings and collaborative sessions ensure all team members are aligned and working toward the same objectives.
Scalability of the process:
- Maintaining and updating BDD scenarios is a continuous task. You’ll likely need to revisit and refine your scenarios as your project changes.
Efficient test automation:
- A high-level of thought and planning goes into efficiently automating BDD tests.
- Look for ways to reuse test steps, and consider using a BDD framework that easily integrates with your existing automation tools.
Continuous process improvement:
- Like any other process, BDD is not a set-and-forget activity.
- Regularly evaluate your BDD processes, solicit feedback from team members and stakeholders, and iterate as needed.
Solis and Wang (2011) conducted a study entitled “A Study of the Characteristics of Behaviour Driven Development” at the 37th EUROMICRO Conference on Software Engineering and Advanced Applications. This paper provides excellent insight into BDD characteristics and best practices. It can be helpful for teams that want to optimize their BDD process.
Final Takeaways
BDD revolutionizes software development by promoting collaboration and clear communication. It closes the communication gap between technical and non-technical stakeholders, aligning everyone involved in the process.
In my experience, teams that implement BDD experience higher product quality and fewer miscommunications. You’re ready to use BDD in your projects. Just remember that it’s a journey of ongoing learning and iteration. The most important thing is to start small, iterate, and optimize your strategy as you go.
