Behavior Driven Development (BDD) -- Bridging the gap between Business and Software Testing
Published: 2023-09-07 23:20:24

by [Sarah Okolo](https://blog.openreplay.com/authors/sarah-okolo)

<blockquote><em>Behaviour-Driven Development, commonly referred to as BDD, is a method used in software development to align software development process with its business requirements. This method aims to facilitate better communication between the technical and non-technical team members involved in software development by providing a common language to express and understand the different software requirements. This article will introduce BDD and explain its principles, motivations, and methodology.</em></blockquote>


Around 2006, a software developer named [Dan North](https://dannorth.net/about/), an expert technology and organizational consultant, first introduced the idea of Behavior-Driven Development (BDD). In an [influential article](https://dannorth.net/introducing-bdd/), Dan North shed light on the benefits of BDD and its potential to enhance collaboration and understanding among stakeholders. He recognized that by shifting the focus from isolated unit tests to higher-level behavioral specifications, teams could foster improved collaboration and align development efforts with business goals. This paradigm shift in mindset paved the way for adopting BDD as a powerful approach to software development.
Now that we have explored the origins and motivations behind Behavior-Driven Development (BDD) let's take a look at some of its key principles
## Key Principles and Goals of BDD
Behaviour-Driven Development has been embraced by the software development community for a considerable period of time. Over the years, practitioners and thought leaders have identified foundational principles defining BDD's essence and contributing to its success.
Here are some of the core principles and goals that make BDD a powerful approach in software development today:
- **Early Validation and Feedback**: BDD promotes the creation of acceptance criteria and scenarios early in the development process. These scenarios act as executable specifications, allowing stakeholders to validate and provide feedback on the system's behavior before investing significant development effort. By incorporating feedback iteratively, BDD ensures that the software aligns with customer expectations throughout the development lifecycle.
- **Improved Collaboration and Communication**: BDD encourages active participation and effective communication between business analysts, developers, testers, and clients. By fostering collaboration, BDD ensures that everyone has a shared understanding of the software's behavior.
- **Use of Common Language(Gherkin)**: Gherkin is a human-readable language used to write structured scenarios in BDD; it provides a structured syntax with keywords like `Given`, `When`, and `Then`. This shared language makes it easier for technical and non-technical team members to communicate and align their understanding of the software's expected behavior. Gherkin is not specific to any programming language and can be used with various BDD frameworks
Let's take a look at a simple example scenario written using the Gherkin syntax:
``` gherkin
Feature: User Authentication
 As a user
 To access my account
 I want to be able to log in with my pre-registered credentials
Scenario: Successful Login
 Given I am on the login page
 And I have a pre-registered account
 When I enter a valid username and password
 And I click the login button
 Then I should be redirected to the dashboard page
 And I should see a welcome message with my name

Scenario: Failed Login
 Given I am on the login page
 And I have a pre-registered account
 When I enter an incorrect account username and password
 And I click the "Login" button
 Then I should see an error message "Invalid credentials. Please try again."
```
In this example, the `Scenario` describes the desired behavior of the user authentication feature. It starts with a `Feature` description, followed by a specific scenario within that feature. The scenario outlines the steps and expected outcomes for a successful and failed login process.
This scenario, written in Gherkin syntax, provides a clear and structured representation of the behavior to be tested and serves as a foundation for collaboration and shared understanding among stakeholders. The written scenarios are typically stored in a file known as a "feature file" or "specification file", which is usually a simple text document. These files serve as living feature documentation in the project's directory.
- **Ensure Customer Satisfaction**: BDD emphasizes aligning the software's behavior with the needs and expectations of the end users. By focusing on user stories and scenarios, BDD encourages developers to understand the customer's requirements deeply. This user-centric approach ensures that the final product addresses the actual needs of the customers, leading to greater satisfaction.

## Essential steps required for BDD implementation in your development process
Implementing Behavior-Driven Development (BDD) involves several key steps crucial for its successful implementation. Let's discuss these steps:
1. **Proper Communication**:
- Engage with stakeholders, developers, testers, product owners, and business analysts.
- Conduct collaborative meetings and workshops to gather requirements and define expectations.
- Facilitate open communication channels to ensure a shared understanding of the desired behavior.
2. **Identifying features and scenarios**:
- Identify the key features or functionalities of the system or application under development.
- Break down these features into smaller, manageable scenarios that capture specific behaviors.
- Prioritise and define the acceptance criteria for each scenario.
3. **Writing GWT-style scenarios**:
- Structure and write the scenarios using the Given-When-Then (GWT) format.
- Start with a clear description of the initial state (Given).
- Specify the action or event that triggers the behavior (When).
- Define the expected outcome or behavior (Then).
4. **Mapping scenarios to code**:
- Create a mapping between the written scenarios and the corresponding code implementation.
- Ensure each scenario is associated with the relevant unit tests or automation scripts.
- Maintain traceability between the scenarios and the codebase.
5. **Executing and automating scenarios**:
- Execute the scenarios manually to validate the behavior of the system.
- Automate the scenarios using BDD frameworks and tools like Jasmine or Cucumber.
- Implement automated tests that verify the expected behavior based on the defined scenarios.
6. **Analysing and reporting test results**:
- Monitor the execution of the scenarios and collect test results.
- Analyse the test results to identify any failures or issues in the system.
- Generate comprehensive reports that provide visibility into the test coverage, pass/fail status, and any defects or issues discovered.
These steps outline a practical approach to implementing BDD, highlighting the importance of collaboration, scenario definition, code mapping, test execution, and result analysis in the BDD workflow.

## BDD compared to TDD, ATDD, and other development models
You may ask yourself, "Well, what makes BDD so different from TDD and other development models?" The answer lies in BDD's unique approach towards testing and collaboration by focusing mainly on the business and user aspects of software development. Understanding these differences will help you make informed decisions about which approach best suits your development needs.
Let's start with [Test-Driven Development (TDD)](https://en.wikipedia.org/wiki/Test-driven_development), a popular methodology that focuses primarily on writing tests before writing the actual code. TDD ensures that the code meets the desired behavior by writing tests that exercise different parts of the codebase. This approach promotes code quality and reduces the chances of bugs. However, TDD primarily addresses the development aspect and may not provide a direct link to business requirements.
On the other hand, [Acceptance Test-Driven Development (ATDD)](https://en.wikipedia.org/wiki/Acceptance_test-driven_development) brings stakeholders, such as business experts, developers, and testers, together to define acceptance criteria and tests based on the desired software behavior. It's like a team brainstorming session for an exciting project. ATDD ensures everyone is on the same page, aligning development with business expectations. However, ATDD typically uses a more technical language to define acceptance criteria and tests. While it may involve collaboration with business stakeholders, the emphasis is on defining testable requirements rather than a shared language, so it may lack a clear link between the business requirements and the underlying code.
Now, let's dive into Behavior-Driven Development (BDD), a methodology that stands out for its strong emphasis on collaboration, communication, and understanding the desired behavior from a business perspective. BDD takes the best elements from TDD and ATDD and adds a layer of clarity and context. It's like attending a magic show, where the magician shows you the trick and explains the logic behind it.
In BDD, you start by identifying and understanding the business requirements. This step involves collaborating with stakeholders to clearly understand what the software should achieve. By involving stakeholders early on, BDD ensures everyone is on the same page and the software aligns with the desired business outcomes.
Next, you translate these requirements into user stories, concise descriptions of feature functionalities from an end-user's perspective. A user story is a communication tool between the business and development teams, providing context and clarity and enabling the development team to better understand the desired behavior.

What sets BDD apart is the creation of scenarios written in a business-readable format. These scenarios become executable specifications, driving development and testing efforts while maintaining a clear link to the underlying code. Scenarios describe different possible interactions with the software, and the development team, testers, and business stakeholders collaboratively develop them.
In breaking down acceptance criteria into executable scenarios, BDD creates a shared understanding of the expected behavior. This shared understanding bridges the gap between technical and non-technical team members, resulting in improved collaboration and more accurate testing. Developers write the code to make these scenarios pass, while testers execute them to ensure that the software behaves as intended.

| Aspect | BDD | TDD | ATDD |
| ------ | --- | --- | ---- |
| Focus on | Behavior | Code | Acceptance Criteria |
| Language | Business Language (eg., Gherkin ) | Programming language | Natural Language |
| Collaboration required between | Developers, testers, business analysts and stakeholders | Developers and testers | Developers, testers, and stakeholders |
| Test Granularity | End-to-End tests | Unit tests | Acceptance Tests at the Feature/Story level |
By adopting BDD, businesses can align their development efforts with business objectives, enhance team collaboration, and deliver software that truly meets the needs of stakeholders.


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## Choosing the right BDD tools and frameworks for your project
When it comes to implementing Behavior-Driven Development (BDD), choosing the right tools and frameworks is crucial for the success of your project. These tools and frameworks play a significant role in enabling collaboration, automating scenario execution, and ensuring efficient BDD practices. Let's delve into the considerations and factors to consider when selecting the appropriate BDD tools and frameworks for your project.
 
- **Language and Technology Stack**: Start by considering your project's programming language and technology stack. BDD tools and frameworks often have language-specific implementations, so choosing a tool compatible with your project's technology stack is essential. For example, if you're working with Java, you might consider tools like [Cucumber](https://cucumber.io/) and [JBehave](https://jbehave.org/), whereas if you're using JavaScript, you might explore options like [Cucumber.js](https://cucumber.io/docs/installation/javascript/) or [Jasmine](https://jasmine.github.io/). For Python, an options like the [behave](https://behave.readthedocs.io/en/latest/) framework is a better option, as it is specifically designed for the language.
- **Documentation and Collaboration**: BDD emphasizes collaboration and clear communication between different stakeholders. Therefore, selecting a tool that facilitates collaboration and provides comprehensive documentation features is crucial. Look for tools that support collaboration features such as shared repositories, version control, and the ability to easily share and discuss scenarios and specifications. Documentation features like auto-generated living documentation or integration with documentation platforms can also be beneficial.
- **Integration and Extensibility**: Evaluate the integration capabilities of the BDD tools and frameworks with your existing development and testing ecosystem. Check if the tools can easily integrate with your preferred IDE, continuous integration/continuous deployment (CI/CD) systems, test runners, and other relevant tools. Additionally, consider the extensibility of the tools. Can you easily create custom plugins or extensionsto cater to specific project requirements?
- **Community Support and Active Development**: Consider the vibrancy of the community surrounding the BDD tools and frameworks you are considering. An active community ensures ongoing development, bug fixes, and tool support. Look for active forums, mailing lists, and GitHub repositories. The availability of regular updates and releases indicates that the tool is actively maintained and supported.
- **Enterprise-level Features**: Consider tools that offer enterprise-level features for larger projects or enterprise environments. These may include features like user access control, scalability, integration with project management tools, and support for distributed teams. Such features can enhance collaboration, security, and efficiency in managing BDD processes within larger organizations.
By carefully considering these factors, you can select the BDD tools and frameworks that best align with your project's requirements and facilitate effective collaboration, automation, and reporting. Remember that the choice of tools should ultimately support your team in achieving the goals of BDD, fostering collaboration, and ensuring the delivery of high-quality software that meets the desired business outcomes.

## Best practices for successful BDD implementation
Implementing BDD effectively requires following certain best practices. By adhering to these practices, you can maximize the benefits of BDD and ensure successful implementation. Here are some key best practices to consider:
 
- **Business-Readable Scenarios**: Focus on creating scenarios easily understandable by technical and non-technical team members. Use clear and concise language that reflects the desired behavior from a business perspective. Involve business experts in reviewing and validating the scenarios to ensure accuracy.
- **Clear Acceptance Criteria**: Define explicit and unambiguous acceptance criteria for each scenario. These criteria should outline the conditions that must be met for a scenario to be considered successful. Well-defined acceptance criteria provide a solid foundation for development and testing efforts.
- **Test Automation**: Automate the execution of BDD scenarios whenever possible. This enables frequent and efficient testing, improves the speed of feedback loops, and reduces the risk of human error. Use appropriate testing frameworks and tools that support BDD automation, such as Cucumber or Jasmine.
- **Cross-Functional Collaboration**: Encourage collaboration and knowledge-sharing between different roles and disciplines within the team. Developers, testers, and business experts should work closely to understand requirements, clarify scenarios, and ensure that the software meets business expectations.
- **Regular Refinement and Improvement**: Continuously refine and improve your BDD implementation based on feedback and lessons learned. Regularly review and update scenarios and acceptance criteria to reflect evolving business needs. Encourage retrospectives and feedback sessions to identify areas for improvement and implement necessary adjustments.
- **Measure and Monitor**: Establish appropriate metrics to measure the effectiveness of your BDD implementation. Track key indicators such as scenario coverage, defect rates, and stakeholder feedback. Monitor the impact of BDD on software quality, team collaboration, and overall project success.
Following these best practices can create a strong foundation for successful BDD implementation. Remember that BDD is not just a technical process but also a mindset that promotes collaboration, shared understanding, and customer-centric development. Embrace these principles, adapt them to your project's context, and iterate based on feedback to continually improve your BDD implementation.

## Practical implementation of BDD in Javascript using the Jasmine framework
Jasmine is a popular JavaScript testing framework that provides an expressive syntax for writing tests in a behavior-driven style. It's a good fit for BDD implementation in JavaScript because it promotes readability and clarity in test specifications and aims to be fast and work right out of the box. It was first released in 2010 and can be used to test both synchronous or asynchronous, front- or back-end, Javascript code. To get started, first, we need to set up the Jasmine framework for our development.
- Step 1: **Installing Jasmine**: To begin, we must install Jasmine and its dependencies in our development environment. You can use [npm (Node Package Manager)](https://nodejs.dev/en/learn/an-introduction-to-the-npm-package-manager/) to install Jasmine globally by running the following command in your terminal:
```
npm install -g jasmine
```
This command installs Jasmine as a global package, allowing you to use it in any JavaScript project.
After the installation is complete, you can verify if "Jasmine" is installed correctly by running the following command:
```
Jasmine -v
```
This should display the version of "Jasmine" installed on your system, which should be the latest version.
- Step 2: **Initializing Jasmine**: Once Jasmine is installed, we can initialize it within our project's directory. Run the following command in your terminal:
```
jasmine init
```
This command will create the necessary files and directories for a Jasmine project, including a ` spec `directory to store your test specifications.
* Step 3: **Writing BDD Scenarios**: Now, let's look at a very basic practical example to fully understand how we can incorporate BDD in our testing using Jasmine.
Consider a simple scenario where we have a ` sum `function. We want to ensure that the function correctly adds two numbers together.
Firstly, we write out the specifications using the gherkin syntax:
```gherkin 
Feature: Addition Calculator
 As a user
 To perform addition calculations
 I want to be able to add two numbers
 Using the sum function.
 Getting the accurate result.
Scenario: Adding two numbers
 Given I enter the numbers 5 and 7
 When I call the sum() function
 Then the result should be 12
```
In this Gherkin scenario, we specify the behavior of adding two numbers using the `sum` function. The `Given` step sets up the initial context by stating the action of entering the numbers 5 and 7. The `When` step indicates that we call the `sum` method. Finally, the `Then` step asserts that the result of the addition should be 12.
Now, let's go ahead and create our little addition function in our calculator.js file in the projects directory itself and make sure to export the function, so it can be called in other files: 
```javascript
//calculator.js
function sum(a, b) {
 return a + b;
}
module.exports = sum;
```
Next, in the `spec` directory created by Jasmine, we create a new file called `calculatorTest.js`. This file will contain our test specifications.
```javascript
//calculatorTest.js
const sum = require('../calculator');
describe("Calculator", function() {
 it("should correctly add two numbers", function() {
  let result = sum(2, 3);
  expect(result).toEqual(5);
 });
})
```
In this example, firstly, we import the `sum `function from the `calculator.js` file in the parent directory. Ensure that the file paths in the `require` statement match the actual path to the code file you choose to test.
We then use the `describe` function to define a test suite for the `sum `function. The `it `function defines an individual test case. In this case, we specify that the `sum `function should correctly add two numbers. We call the function with the arguments `2` and `3` and use the `expect` function to assert that the result should equal `5`.
- Step 4: **Running Tests**: To run the Jasmine tests, execute the following command in your terminal:
```
jasmine
```
Jasmine will execute the test specifications defined in the `spec` directory and display the test results in the terminal. So for our example code above, this would be the output printed out…
![jasmine test case passed successfully](https://blog.openreplay.com/images/behavior-driven-development-bdd-bridging-gaps/images/image2.png)
This shows that the single test case that we specified passed successfully.
- Step 5: **Iterating and Expanding Scenarios**: You can continue to iterate on your BDD scenarios by adding more test cases and refining your specifications. For example, you might add additional tests to verify edge cases, handle error conditions, or test different application functionalities.
```javascript
it("should handle negative numbers", function() {
  let result = sum(-2, 3);
  expect(result).toEqual(1);
 });
 it("should return the initial number when adding zero to a number", function() {
  let result = sum(5, 0);
  expect(result).toEqual(5);
 })
```
In the above examples, we added two new test cases. The first test case verifies that the `sum `method correctly handles negative numbers. The second test case ensures that adding zero to a number returns the same number. Now let's run the test and check out the output:
![Additional jasmine test cases passed successfully](https://blog.openreplay.com/images/behavior-driven-development-bdd-bridging-gaps/images/image3.png)
We can see now that all three of our test cases passed successfully. How about if an error is encountered during the testing? Let's look at an example by creating a little trigger error. Let us replace a number in one of the test cases with a letter instead; since we know we cannot add a number with a letter, this should bring up an error.
```javascript
describe("sum", function() {

it("should correctly add two numbers", function() {
  let result = sum(f, 3);
  expect(result).toEqual(5);
 });
})
```
In this code, we have changed the number 2 value in the sum function with the letter f. Now, let us rerun the test to see the result:
![Failed Jasmine Test](https://blog.openreplay.com/images/behavior-driven-development-bdd-bridging-gaps/images/image1.png)
We can then see that three tests are recorded, but only two passed and one failed, which is the test case we just modified, so if any of your code does not pass the test, these are the error messages you would encounter.
By following this approach, you can create an extensive suite of BDD scenarios using Jasmine, covering various aspects of your application's functionality.

## Pros and cons of BDD
Behaviour-Driven Development (BDD) offers several advantages and has certain considerations to remember. Let's explore the pros and cons of BDD:
### Pros of BDD
- **Living Documentation**: BDD scenarios serve as living documentation, providing a clear and up-to-date understanding of the system's behavior. They serve as executable specifications, enabling stakeholders to validate and verify the system's behavior.
- **Shared Understanding**: BDD fosters shared understanding, aligning the development team with the business goals and requirements.
- **Clarity and Readability**: BDD scenarios are written in a human-readable language that can be easily understood by technical and non-technical team members. This improves clarity and reduces ambiguity in requirements and test specifications.
- **Customer Focus**: BDD strongly emphasizes delivering business value and satisfying customer needs. By focusing on behavior and outcomes, BDD ensures that software development efforts align with the desired business outcomes.
- **Early and Continuous Testing**: BDD encourages testing early in the development process. By defining test scenarios upfront, BDD helps identify and address potential issues at an early stage, reducing the cost and effort of fixing defects later.
### Cons of BDD
- **Time and Effort**: Writing detailed scenarios and maintaining them can require additional time and effort compared to traditional testing approaches. Teams must invest in defining clear specifications and maintaining them throughout the project.
- **Over-engineering**: There is a risk of over-engineering scenarios, resulting in overly complex and cumbersome test specifications. Teams must strike a balance between providing sufficient coverage and avoiding unnecessary complexity.
- **Tooling and Infrastructure**: BDD implementation often requires specialized tools and frameworks. Teams must invest in establishing and maintaining the necessary infrastructure and integrating BDD practices into their development and testing workflows.
- **Collaboration Challenges**: BDD relies heavily on effective collaboration between business and technical stakeholders. Ensuring consistent and regular collaboration can be challenging, particularly in large or distributed teams.
- **Business Expert Availability**: BDD scenarios heavily rely on input from business experts to define and validate requirements. The availability and engagement of business experts may impact the speed and effectiveness of the development process.
Overall, the benefits of BDD, such as improved collaboration, customer focus, and test automation, make it a valuable approach for many development teams. However, teams should consider the learning curve, the effort required for scenario definition, and the need for effective collaboration when adopting BDD in their projects.

## Conclusion
By aligning business requirements, development, and testing through the use of human-readable scenarios, BDD fosters shared understanding and enhances the quality of software solutions. Throughout our exploration of BDD, we've discussed its key principles, implementation steps, comparison with other development models, and the selection of suitable tools and frameworks.
One key takeaway from our discussion is the significance of effective collaboration and communication among team members. BDD emphasizes the involvement of business experts, developers, testers, and other stakeholders to ensure a shared understanding of requirements and project goals. By fostering open dialogue and encouraging regular feedback loops, teams can create software solutions that truly meet the needs of the business and end-users.
I hope this article has been able to shed some light on the concept of Behaviour Driven Development(BDD), its importance, and how it can be applied in your software development process.