BDD Testing - A Comprehensive Guide

Behavior-Driven Development (BDD) is a collaborative approach to software development that bridges the gap between technical teams (developers and testers) and non-technical stakeholders (business analysts, product owners). It’s designed to ensure that software behaves as the stakeholders intend by focusing on how users interact with the system.
In this guide, we will go over the core aspects of BDD, how it works, its principles, the tools that support it, and its advantages over other methodologies like Test-Driven Development (TDD).

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What is BDD?

Behavior-driven development (BDD) is an evolution of Test-Driven Development (TDD). In TDD, the process begins by writing test cases for small units of code before writing the code itself. BDD takes this idea further by involving non-technical stakeholders in the test design process, focusing on the system's expected behavior from the user's perspective.

bheavior-driven-development

In BDD, the software's behavior is expressed through scenarios written in plain language, typically using a structured syntax called Gherkin. These scenarios are then automated into tests. For example:

bdd-example

How does BDD work?

BDD works through continuous collaboration between developers, testers, and business stakeholders. The goal is to write test scenarios that represent real-world behavior. These tests validate the system's correctness and serve as living documentation, which is useful for understanding how the system should behave.

bdd-process

Let’s break down the steps involved in the BDD process:

1. Define User Stories: The first step is understanding what the user needs and translating that into user stories. A user story represents a small piece of functionality from the perspective of the user. For example:

As a user, I want to be able to log into my account so I can access my personal dashboard.

2. Write Scenarios in Gherkin: After defining the user stories, the next step is to write Gherkin scenarios that outline how the system should behave in different situations. Gherkin syntax uses keywords like Given, When, Then, and And to structure scenarios clearly:

Given: Specifies the initial context or setup.
When: Specifies the event or action.
Then: Specifies the expected outcome.

Continuing with the login example, a Gherkin scenario could look like this:

gherkin-scenario-example

3. Automate the Scenarios: Once scenarios are written, developers convert these plain language scenarios into automated tests using BDD frameworks like Cucumber, SpecFlow, or Behave. These tools parse the Gherkin syntax and map it to test code that interacts with the application.

4. Run the Tests: These automated tests are run frequently, ensuring that the system’s behavior matches the intended behavior as new code is added or existing code is modified.

5. Refine and Iterate: As development progresses, the scenarios are updated and refined to reflect new requirements or changes in the system’s behavior. This creates a feedback loop where the behavior is constantly validated and documented.

Key principles of BDD

Collaboration: One of the foundational principles of BDD is collaboration among developers, testers, and stakeholders. The scenarios are written in a way that all team members, regardless of their technical expertise, can understand and contribute to the conversation about how the system should behave.
Focus on Behavior: BDD emphasizes behavior rather than implementation. The goal is to describe what the system should do from the user's perspective rather than how it should be built. This shifts the focus from technical details to the overall user experience.
Ubiquitous Language: BDD encourages the use of a common language between the business and technical teams. By using Gherkin syntax, BDD scenarios serve as a single source of truth, bridging the gap between business requirements and technical implementation.
Living Documentation: BDD scenarios act as living documentation. Since these scenarios are automated tests, they provide an up-to-date record of how the system behaves. This is a major advantage over traditional documentation, which often becomes outdated as the system evolves.
Test Automation: Automating the scenarios ensures that the behavior of the system is continuously validated as code changes are made. This helps catch regressions early and ensures the system behaves as expected over time.

Illustrative Example of BDD in Action

Let’s take an e-commerce website that needs to implement a new feature allowing users to search for products. Using BDD, the team would first discuss the feature with stakeholders and create user stories such as:

As a customer, I want to search for products by name so I can find items quickly.

After defining the user stories, the team would write Gherkin scenarios like:

bdd-in-action-example

This scenario describes the expected behavior from the user’s perspective, making it clear what needs to be developed. The developers can now automate this scenario into a test and ensure that the search functionality behaves as described.

Benefits of BDD

Enhanced Communication: Since BDD uses plain language and encourages collaboration, it ensures that everyone on the team understands the system’s behavior. Business stakeholders can contribute to defining the scenarios, leading to fewer misunderstandings.
Alignment with Business Goals: Because the focus is on behavior, BDD ensures that the software being developed meets the actual needs of the users and aligns with business goals.
Fewer Defects: By defining clear scenarios and automating them as tests, BDD helps catch issues early in the development process, reducing the number of defects that reach production.
Living Documentation: As mentioned earlier, BDD scenarios act as living documentation. This reduces the overhead of maintaining separate documentation and ensures that everyone on the team has an up-to-date understanding of the system’s behavior.
Easier Refactoring: With automated tests in place, developers can refactor code with confidence, knowing that the behavior of the system is constantly being validated.

bdd-advantages

Drawbacks of BDD

Initial Overhead: Writing comprehensive BDD scenarios can be time-consuming, especially in the early stages of a project. Teams need to invest time in learning the syntax and agreeing on the scenarios.
Collaboration Challenges: BDD relies on strong collaboration between business and technical teams. If stakeholders are not engaged or available, the benefits of BDD can be diminished.
Scalability Issues: Managing and maintaining these tests can become tiring in large projects with hundreds or thousands of scenarios. Over time, some scenarios may become outdated or redundant, requiring regular maintenance.
Over-Testing: There’s a risk of writing too many scenarios that test minor details, leading to an overwhelming number of automated tests that can slow down the development process.

Best practices for BDD

Start Small: It’s important to begin with a few key features and avoid overloading the process with too many scenarios at the start. As the team becomes more comfortable with BDD, they can expand the scope.
Write Clear and Concise Scenarios: Each scenario should be focused on a specific piece of functionality. Avoid combining multiple behaviors in a single scenario, as this can make the tests harder to understand and maintain.
Prioritize Collaboration: The success of BDD depends on close collaboration between technical and non-technical team members. Regular discussions and workshops should be held to ensure that everyone is aligned on the system’s behavior.
Review and Update Scenarios: As the system evolves, some scenarios may become obsolete or need adjustments. Regularly review the scenarios to ensure they accurately reflect the current behavior of the system.
Focus on Behavior, Not Implementation: Remember that BDD is about defining how the system should behave, not how it should be built. Avoid writing scenarios that are too focused on technical details.

BDD vs. TDD

BDD and TDD are often compared because they both emphasize writing tests before writing code. However, they have some key differences:

Focus: TDD focuses on writing tests for individual units of code, typically at a technical level. Incontrast, BDD focuses on defining behavior from a user’s perspective.
Language: TDD tests are written in a technical format, while BDD uses plain language (via Gherkin) to describe system behavior.
Collaboration: TDD is primarily a developer-driven process, whereas BDD encourages collaboration with non-technical stakeholders, making the process more inclusive.

Here’s an example of a TDD test for the same product search feature:

bdd-vs-tdd-example

In contrast, the BDD version would focus on the user interaction, as shown in the earlier Gherkin example.

Tools for BDD

Some of the most commonly used BDD tools include:

Cucumber: One of the most popular BDD frameworks, Cucumber supports multiple languages (Java, Ruby, JavaScript) and integrates well with Gherkin. It’s widely used for its simplicity and ability to bridge the gap between business and technical teams.
SpecFlow: A BDD framework for .NET applications. SpecFlow allows developers to write Gherkin scenarios in .NET environments, making it a popular choice for teams working in the Microsoft ecosystem.
JBehave: A Java-based BDD framework that promotes the use of BDD in Java projects. JBehave encourages a narrative-based approach to defining behaviors.
Behave: A Python-based BDD framework that integrates well with Python applications. It uses Gherkin syntax to define scenarios and automates them as tests.
TestProject: A free test automation platform that supports BDD and integrates with a variety of tools. It offers a low-code approach to test automation, making it accessible to teams with varying levels of technical expertise.

Key use cases for BDD

E-commerce: BDD is commonly used in e-commerce applications to define and test user journeys, such as product searches, checkout processes, and payment flows. For example, a scenario might define how a user adds an item to their cart, proceeds to checkout, and completes the purchase.
Banking Applications: BDD can be used in financial applications to validate complex transaction flows. For instance, defining and testing how a user transfers money between accounts or applies for a loan ensures that the behavior meets both user and regulatory requirements.
Healthcare Systems: In healthcare, BDD helps validate features like patient data management or appointment scheduling. Scenarios might describe how a patient schedules an appointment or how doctors access medical records.

Conclusion

Behavior-Driven Development (BDD) is a powerful methodology that improves collaboration, aligns software development with business goals, and ensures that software behaves as intended. By focusing on user-centric scenarios and automating them as tests, BDD helps teams build software that meets the needs of its users and stakeholders.

While it has some challenges, such as the initial learning curve and ongoing maintenance, the benefits of better communication, reduced defects, and living documentation make it a valuable approach for many software projects.

How can Global App Testing help?

Global App Testing (GAT) complements Behavior-Driven Development (BDD) by providing real-world testing that extends beyond automated scenarios defined in BDD. Here's how they relate:

Real-world validation: While BDD tests behaviors in controlled environments, GAT validates those behaviors across different devices, regions, and network conditions. For instance, a BDD scenario might pass locally, but GAT can reveal issues like slow performance or localization bugs in real-world conditions.
Crowdsourced testing: BDD defines specific scenarios, but GAT leverages global testers to find edge cases and unexpected issues that predefined scenarios might miss. This ensures that both planned and unforeseen problems are addressed.
User perspective: BDD focuses on collaboration between developers and stakeholders to define behavior, but GAT brings in feedback from real users across different cultures and environments, highlighting usability and localization issues that automated tests might miss.
Continuous feedback: Both BDD and GAT promote continuous improvement. While BDD scenarios are refined as features are developed, GAT provides ongoing feedback from global users, ensuring that behaviors remain consistent across regions as the app evolves.
Human insights: BDD automates behavior testing, but GAT offers human insights into areas like usability, performance, and device-specific bugs. This combination of automation and human feedback enhances software quality.

Ready to take your testing strategy to the next level? Contact Global App Testing today and see how we can help you deliver flawless software on a global scale!