Behavior Driven Development - Definitive Guide
Tags: testing, bdd, automation, webdev
Published: 2023-09-13 11:30:40

Although the traditional waterfall development approach is still very much around, [PMI’s survey](https://www.pmi.org/-/media/pmi/documents/public/pdf/learning/thought-leadership/pulse/pulse-of-the-profession-2017.pdf) puts the percentage of companies that have adopted the agile methodology at 71%. Clearly, executing the project phases using the agile approach doesn’t only improve user experience and speed up product launch. But it also enhances a company’s revenue growth.

Behavior-driven development (BDD) is a popular agile methodology among many companies today. What is BDD, and why should companies use it? How does it work in agile methodologies? 

## What is behavior driven development (BDD)?

Behavior-driven development is a software development approach that focuses on making the final software work to meet customers’ expectations. BDD is customer-driven and highly collaborative. It involves effective communication between the product owner, developers, testers, operations team, and customers to ensure that software ships to the end user in its best quality. 

During BDD, the testers develop the test suite around the expected customers’ behavior, as defined by the product owner or consumer insight team. This user-focused strategy improves user experience and overall market adoption. 

## How behavior driven development works

Here’s how to conduct an effective BDD:


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/4043dwx1eysd5cw0ji7e.jpeg)


- **Develop comprehensively detailed user stories:** The first step in BDD involves conducting [data-driven](https://testsigma.com/automated-data-driven-testing) customer insight analysis. This helps the product owner and all stakeholders to understand the application's expected features and how the users interact with them. This stage requires adequate brainstorming to ensure the final product stays within the business goal.

- **Document the user stories:** The next phase is to write down the identified users' stories [using a structural plain language like Gherkin](https://testsigma.com/blog/behavior-driven-development-bdd-with-gherkin/). This is where the "Given-When-Then" structure comes in.

- **Collaborate with the entire team:** It's essential to maintain collaboration across the team to effectively communicate the user stories to the developers, stakeholders, testing team, and operations team. This ensures that everyone is on board with the product's expected output.

- **Build an automated test scenario:** In this case, the testers convert the user stories into automated test cases.
Run the software code against the developed test scenarios: Since the test suite is user-centric, this phase checks if the application meets the users' personas as tested in the suite.
 

- **Resolve behavioral drifts and create a feedback loop:** If the application fails some test scenarios, this implies deviation from users' satisfaction. The team must develop a strategy for patching these changes. Regardless, this stage also requires the team to get adequate feedback from customers and stakeholders. This helps build confidence and improves overall software behavior. 

- **Set up test management and monitoring:** For better transparency, set up your entire test management and monitoring. For this, test automation tools that enable the same can be used.

## Key advantages of Behaviour Driven Development

### Customer-driven product development

Rather than building a product that only meets the developers’ specifications, BDD ensures that the outcome of the development process satisfies the ideal end-users.

### Proper prioritization of features

The product owners and other stakeholders brainstorm and pore through the user stories to identify and prioritize the key functionalities that affect business logic.

### Greater transparency

BDD carries every member of the team along during the process and using a feedback loop to assess how the product serves the ideal users, aids in transparency.

### Reduced maintenance and project risk

Since the developers run the application against a pre-written user-centric test suite, they can determine the expected behavior of each component upfront and mitigate any discrepancies while building the application. This way, they get to fix bugs before each release, reducing the time and resources needed to maintain the app in production.

### Better alignment with overall business goals

In BDD, test scenarios and business logic rely on defined user stories. Hence, the development team builds the business logic to align with the specified business goals.

## Behavior Driven Development Examples

BDD generally adopts the “Given-When-Then” format to develop users’ stories for a software product. Once a user story is available, it becomes easier for the developers to build an automated test scenario around the identified user stories. The automation test still follows the [elemental principles of automated testing](https://testsigma.com/blog/principles-of-software-test-automation/) to execute the scenarios during Behaviour Driven Development.

Once the team tests the user stories, the development team repurposes the functionality code base to meet the test behavior and users’ specifications. Before sighting an example, let’s briefly see how the “Given-When-Then” format works.

## The Given-When-Then approach


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/6xrjl7fk6nzkb1cgc9n3.jpeg)

The Given-When-Then approach is a BDD structural format for developing test scenarios around user stories.

**Given:** This begins a user story for a specific scenario. Here, you develop a set of pre-conditions for an event.

**When:** This is where an event is triggered based on the given situation. It defines a user’s expected action given the existing condition.

**Then:** Every action has a result. The “then” part describes the expected outcome based on the triggered event.

Using an e-commerce website as an example, below is a BDD approach that uses the “Given-When-Then” formula based on the provided scenario:


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/zl49je60psrh7ezwfvuq.png)

## BDD and other development and testing methodologies

Although BDD is quite popular among companies using the agile methodology, you might combine it with other approaches to develop a more inclusive and effective application. Let’s discuss some of these methodologies briefly.

### Test-first approach

The test-first approach, or test-driven development (TDD), is an agile method where the developers write the test first and run the implementation code against it. Unlike BDD, the test-first approach does not account for user stories.
 
Instead, it aims to build the software to meet code quality and improve software design based on developers' specifications. After running the functionality code against the unit test, the developer refactors the code and reruns the test. 

This continues iteratively until the code and design meet the required specifications. However, the development team can combine this with BDD to ensure the software suits the business logic and users' expectations and uses optimal code quality.

### Agile testing approach

The agile testing approach is a testing design that follows the agile development principles. It involves iterative, continuous, and collaborative testing along with the development of each feature. In agile testing, each test verifies a specific component or functionality iteratively until shipping. 

BDD is an agile development approach since it fosters collaboration among all stakeholders, the testing, and the DevOps team. Implementing this approach further in BDD builds confidence in the product and lets you test your scenarios iteratively as the software development progresses.

### Built-in quality approach
 
The built-in quality approach is a set of principles that guide the agile development team, ensuring that they build quality into the software from the onset at every development stage. Hence, the product quality is monitored right from the beginning rather than later during the development phase. 

It begins with a thorough understanding of the software's specifications, followed by agile testing and continuous bug fixes. Like BDD, the built-in quality approach involves collaboration between the testing and the DevOps team. And it can combine TDD and BDD principles to ensure quality delivery.
Introducing a new functionality to a system with BDD
You might need to scale your application’s functionality at some points during software development. 

Functionality introduction with BDD generally involves three steps:

#### The discovery phase

At this stage, you Identify the need to add new functionality and highlight its use cases.
Gather the initial information needed to develop a test scenario around the new feature. Brainstorm to understand the test requirements and determine the scopes and objectives of the automation.

#### Formulation phase

In this phase, you document all the possible ways a customer can use the added functionality such that you can automate it. The testing team then designs the automation test flow, including how to handle the test data.

#### Automation phase

Develop and execute the test automation based on the documented scenario and use the automation as a development guideline.

## Alternate to BDD

While BDD follows the “Given-When-Then” format, user stories can also be automated easily using tools that allows automation in simple English. They are not constrained by only one format. One example of  a tool that allows you to automate your tests for user stories in simple English is Testsigma.

## Conclusion

Behavior-driven development enhances team collaboration and transparency throughout the development process. User prioritization yields higher revenue since the product caters to the ideal customers. While BDD may not align with the developers' standard of writing quality code, it helps reduces their development workload, as they detect bugs earlier and only focus on the business goal.