Behavior-Driven Development (BDD) scenarios are a pivotal part of BDD methodology. They are used to define the expected behavior of a software system from the user’s perspective. BDD scenarios follow the Given-When-Then format and serve as a clear and structured way to specify how the software should behave in different situations. Here’s how to write BDD scenarios:
1. Understand the Feature or User Story:
Before you begin writing BDD scenarios, it’s crucial to have a clear understanding of the feature or user story you are working on. You should know the specific behavior you want to define.
2. Use the Given-When-Then Format:
BDD scenarios are typically structured using the Given-When-Then format, which helps create a clear and concise description of the expected behavior.
- Given: Describes the initial context or state of the system before the behavior is tested. It sets up the preconditions for the test.
- When: Describes an action or event that occurs, typically triggered by the user or some external factor. This is the action you are testing.
- Then: Describes the expected outcome or behavior resulting from the action defined in the “When” section.
3. Be Specific and Concrete:
Your scenarios should be specific and concrete, leaving no room for ambiguity. Avoid vague or general descriptions. The more precise your scenarios are, the easier they are to understand and implement.
4. Use Plain Language:
BDD scenarios should use plain language that is easily understandable by both technical and non-technical team members. Avoid using technical jargon or complex terminology.
5. Include Context in the “Given” Section:
The “Given” section is where you set up the initial conditions or context for the scenario. This section should establish the state of the system or any necessary preconditions for the scenario to make sense. For example:
- Given the user is logged in
- Given the user has a balance of $100 in their account
6. Describe Actions in the “When” Section:
The “When” section is where you describe the action or event you are testing. This is typically the action that a user takes. For example:
- When the user clicks the “Submit” button
- When the user enters their login credentials
7. Define Expected Outcomes in the “Then” Section:
The “Then” section is where you specify the expected outcomes or results of the action described in the “When” section. This is the behavior you are testing. For example:
- Then the system should display a confirmation message
- Then the user’s account balance should be updated to $150
8. Keep Scenarios Small and Focused:
BDD scenarios should be focused on testing a single aspect of behavior. Keep your scenarios small and specific, addressing one user interaction at a time. This makes it easier to understand, implement, and maintain scenarios.
9. Include Acceptance Criteria:
To ensure clarity and testability, it’s a good practice to include acceptance criteria within or alongside your BDD scenarios. Acceptance criteria provide specific conditions that must be met for the scenario to be considered complete.
Example BDD Scenario:
Here’s an example of a BDD scenario for an e-commerce website:
Scenario: Adding a product to the shopping cart
Given the user is on the product page
And the product "Widget A" is available for purchase
When the user clicks the "Add to Cart" button
Then the user's shopping cart should contain "Widget A"
And the user's shopping cart total should reflect the price of "Widget A"This scenario describes the expected behavior when a user adds a product to their shopping cart.
By following these guidelines, you can write clear, structured, and effective BDD scenarios that accurately describe how the software should behave from the user’s perspective. BDD scenarios serve as the foundation for creating tests and ensuring that your software aligns with user expectations.