Behavior Driven Development, often referred to as BDD, has become one of the most popular approaches in modern software development for bridging the gap between technical and non-technical stakeholders. At its core, BDD focuses on describing how a system should behave using human-readable language. However, within BDD there are two styles of writing scenarios imperative and declarative. Understanding the differences between BDD imperative vs declarative styles can help teams write more effective, maintainable, and understandable test cases. By analyzing both approaches, developers and testers can choose the style that aligns best with their goals, project size, and team dynamics.
Understanding Behavior Driven Development (BDD)
BDD is built upon the idea that software behavior should be defined through examples and scenarios rather than abstract technical requirements. These examples are typically written in Gherkin syntax using keywords such asGiven,When, andThen. The purpose is to make the specifications clear for business analysts, developers, testers, and stakeholders alike.
The Goal of BDD
At its heart, BDD ensures that development is guided by desired business outcomes. Instead of simply focusing on what code does, BDD describes what the software is supposed to achieve. This collaborative approach encourages shared understanding and reduces miscommunication across teams.
What Is Imperative Style in BDD?
Imperative style scenarios in BDD describe behavior by outlining detailed step-by-step actions. This style specifieshowthe system achieves a behavior rather than just stating the expected outcome. Each step tends to be explicit, guiding the execution in a sequence.
Example of Imperative Style
An imperative style scenario might look like this
- Given I am on the login page
- And I enter the username user1″
- And I enter the password “password123”
- When I click on the login button
- Then I should be redirected to the dashboard
Here, the steps are very detailed, describing exactly what actions are taken and in what order. It is procedural and closely tied to the user interface or specific workflows.
Advantages of Imperative Style
- Provides very clear, step-by-step instructions.
- Easy for new testers to understand the sequence of actions.
- Useful when working on UI-heavy applications where user interactions are central.
Disadvantages of Imperative Style
- Can become repetitive across multiple scenarios.
- High maintenance cost if the UI changes.
- Focuses onhowinstead ofwhat, making scenarios harder to read for non-technical stakeholders.
What Is Declarative Style in BDD?
Declarative style, on the other hand, focuses on the behavior and outcomes rather than the detailed steps. Instead of describing exactly how to achieve a result, it describeswhatthe system should accomplish.
Example of Declarative Style
A declarative scenario might look like this
- Given a registered user exists
- When the user logs in with valid credentials
- Then the user should see their dashboard
This version avoids detailing every click or field input. Instead, it communicates the essential business rules in a way that is easy for stakeholders to follow.
Advantages of Declarative Style
- More concise and focused on business behavior.
- Easier for non-technical stakeholders to understand.
- Less fragile since it is not tied to specific UI steps.
- Encourages reuse of step definitions across different scenarios.
Disadvantages of Declarative Style
- May lack detail for testers unfamiliar with the system.
- Sometimes harder to automate because steps are abstract.
- New team members might need additional context to implement automation properly.
BDD Imperative vs Declarative Key Differences
When comparing BDD imperative vs declarative, the core difference lies in how much detail is included in the scenarios. Imperative style emphasizes thehow, while declarative style emphasizes thewhat.
- Level of detailImperative is highly detailed, declarative is high-level.
- ReadabilityDeclarative is more stakeholder-friendly, while imperative can feel technical.
- MaintainabilityDeclarative scenarios are easier to maintain, imperative ones can become brittle.
- FocusImperative focuses on execution, declarative focuses on outcomes.
When to Use Imperative Style
Imperative style is more suitable when a team is focusing heavily on user interface testing, onboarding new testers, or working with systems where exact sequences of actions matter. It is also useful in early stages of BDD adoption when clarity of process outweighs concerns about redundancy.
When to Use Declarative Style
Declarative style works best when the goal is to communicate business requirements to a broader audience. It is also ideal for long-term projects, since it reduces maintenance overhead and keeps scenarios aligned with business logic rather than implementation details.
Blending Imperative and Declarative Approaches
In practice, many teams blend both imperative and declarative approaches. For example, they may use declarative scenarios for documenting core business rules and imperative steps for detailing complex interactions. This hybrid approach allows for both readability and clarity when needed.
Example of a Blended Approach
- Given a registered user exists
- When the user logs in with valid credentials
- Then the system should redirect to the dashboard
- And display the user’s name on the top-right corner
Here, the scenario is mostly declarative but includes specific details when necessary.
Impact on Collaboration
One of the main reasons BDD exists is to foster collaboration. Declarative scenarios tend to serve this purpose better, since they are closer to natural language. Imperative scenarios, while detailed, sometimes alienate non-technical participants. Choosing the right style can therefore directly impact how effectively teams work together.
Automation Considerations
Automation plays a key role in BDD. Imperative steps map easily to test scripts because they describe explicit actions. Declarative steps, however, require abstraction, meaning automation engineers must design flexible step definitions. While declarative scenarios are more elegant, they require a stronger testing framework and more careful planning in automation design.
Choosing between BDD imperative vs declarative styles depends on the team’s goals, the project’s complexity, and the intended audience of the scenarios. Imperative style provides clarity of steps but risks being verbose and fragile. Declarative style offers simplicity, maintainability, and stakeholder readability, though it sometimes leaves gaps in detail. The most effective approach often blends the two, using declarative language for business rules and imperative detail when precision is necessary. Ultimately, understanding the strengths and weaknesses of each style allows teams to write scenarios that are not only executable but also meaningful, aligning software development closely with business needs.