Behaviour Driven Design in Product Development

I've been implementing BDD in my development work for the past few years, and I've found it incredibly useful for improving collaboration between teams and ensuring that what we build actually meets user needs. In this post, I'll walk through how BDD works and how to implement it effectively.

When it comes to test writing, BDD provides a framework for structuring and describing tests in a more human-readable manner. If you're using JavaScript testing with tools like Mocha, Chai, and Should, you can write BDD-style tests using the describe, it, and expect (or should) blocks.

Here's a practical example:

const should = require('chai').should();

describe('Array', function() {
  describe('#indexOf()', function() {
    it('should return -1 when the value is not present', function() {
      const arr = [1, 2, 3];
      const result = arr.indexOf(4);
      result.should.equal(-1);
    });

    it('should return the index when the value is present', function() {
      const arr = [1, 2, 3];
      const result = arr.indexOf(2);
      result.should.equal(1);
    });
  });
});

This test code is straightforward to understand even if you're not deeply technical. Breaking it down:

• The outer describe block defines what component we're testing (the Array object)
• The nested describe specifies which method we're focusing on (#indexOf())
• Each it block describes an expected behavior in plain language
• The assertions verify that the code behaves as expected

What makes this approach so powerful is that product managers and other non-developers can actually read these tests and understand what the system is supposed to do. That alignment between technical and non-technical team members is one of the big wins with BDD.

The Lifecycle of Behaviour Driven Design

If you're considering adopting BDD in your team, it helps to understand the full lifecycle. Here's how it typically works:

1. Discovery

Everything starts with a conversation. You get stakeholders and team members together to define feature behaviors. This is where you gather the insights that will drive your design decisions.

2. Scenario

Next, you translate those discoveries into executable specifications. Instead of jumping straight into code, you create "scenarios" using language everyone understands. The focus is on what your product should do, not how you'll implement it (that comes later).

3. Conversation

The scenarios you've drafted become talking points for dialogue between developers, QAs, and product owners. Everyone works together to refine these scenarios until they accurately capture the user experience and business goals you're aiming for.

4. Automation

Once you've agreed on the scenarios, you turn them into automated tests - and you do this before writing a single line of product code. This is a key point that differentiates BDD from other approaches. You're essentially building a safety net that confirms your product behaves as expected.

5. Implementation

Now (and only now) you write the code to pass those tests. Since the tests are based on predefined behaviors, your development work naturally aligns with user needs.

6. Feedback and Iteration

After release, you monitor usage and collect user feedback. Then it's back to step one, using real-world insights to inform further development.

What I like most about BDD is that it creates a continuous cycle of improvement. You're not just coding features; you're nurturing them from initial concept through to real-world validation, and back again. It keeps your development tightly focused on delivering value to users.

Key Roles and Responsibilities in BDD

In my experience implementing BDD on various projects, I've found that clear roles are crucial to success. When everyone knows their part, the process runs much more smoothly.

Project Manager

The project manager or product owner represents the voice of the customer. Their job is to articulate clear business objectives and prioritize features based on value. They need to define what success looks like and keep the team focused on meeting business needs. They help draft user stories and acceptance criteria that become the foundation for BDD scenarios.

Developers

If you're a developer on a BDD team, you need to understand the system from the user's perspective, not just from a technical angle. You integrate this user-focused understanding into your coding, building features that match user expectations.

Testers

Testers are no longer just checking if the code works - you're collaborating with developers and business stakeholders to define what "acceptable behavior" means for each feature. Then you create automated tests to validate these behaviors, ensuring every code change meets the defined standards.

Facilitator

The facilitator guides everyone through the BDD process, making sure the team understands and follows BDD principles. They help refine user stories and create shared understanding across diverse team members.

Getting these roles to work together effectively can be challenging at first (especially if people are used to more traditional development approaches), but once the team clicks, the results are well worth it.

Writing Effective User Stories and Scenarios

The first time I tried implementing BDD on a project, I struggled with writing good user stories. It took some practice to get them right, but I've found a few principles that consistently work well.

In BDD, user stories and scenarios form the backbone of your development process. A user story isn't a detailed specification - it's a concise narrative that puts you in the user's shoes.

Every good story needs to include:

• The role of the user you're addressing
• The feature or action they need
• The benefit they gain from this feature

For example:

"As a social media manager, I need to schedule posts in advance so that I can maintain a consistent publishing schedule even when I'm away from my desk."

When writing stories, make sure they are:

• Clear: Everyone on your team should understand without ambiguity
• Concise: Keep them brief but detailed enough
• Actionable: Each story should lead to clear development tasks
• Testable: You should be able to create acceptance tests from the story

After creating your user stories, you'll need to detail scenarios - the "what-ifs" that explore different outcomes based on varied inputs and conditions. Each scenario defines:

• A given starting situation
• The action or event that occurs
• The expected outcome

The simplest format (and the one I prefer) is:

"Given [context], when [event/action], then [outcome]."

For example: "Given I have drafted a post, when I click on 'Schedule' and select a future date and time, then the post should appear in my 'Scheduled' list and publish automatically at the specified time."

This structured approach helps everyone understand and test how your product should behave in real-world situations. Well-written user stories and scenarios lead to products that users actually love using.

Integrating BDD with Agile Methodologies

I've worked on several Agile teams, and I've found that BDD integrates really well with Agile practices. It's like adding a turbocharger to your engine - it makes everything run more smoothly and with better results.

If you're using Scrum or another Agile framework, BDD can help bridge the gap between user stories and implementation. It provides a way to ensure everyone is building toward the same vision.

Start by defining clear examples that illustrate how the application should behave. These examples will become your tests, aligning your team's efforts with customer needs.

Next, collaboratively create feature files using the Given-When-Then format. I find it helps to think of it as explaining a feature to a non-technical friend - that's how your functionality descriptions should read.

As developers begin coding, they use these feature files as guideposts. Each passing test brings you closer to the desired outcome. During sprint retrospectives, review your user stories and scenarios. Are they accurately reflecting what users need? Be ready to adjust as your understanding evolves.

The best part of combining BDD with Agile is that it creates a shared language for the entire team. Each sprint becomes a chapter in your product's development story, creating a narrative that everyone can follow and contribute to.

If you've used BDD in your projects, I'd love to hear about your experiences in the comments. What challenges did you face and how did you overcome them?