majiayu000 EARS Format for Acceptance Criteria
EARS (Easy Approach to Requirements Syntax) provides patterns for writing clear, testable acceptance criteria.
WHEN Pattern (Event-driven)
Use for user actions and triggered behaviors.
WHEN <trigger/condition>
THE SYSTEM SHALL <expected behavior>
Example:
WHEN user clicks the submit button
THE SYSTEM SHALL validate all form fields
IF Pattern (Conditional)
Use for state-based conditions and logical branching.
IF <precondition/state>
THEN THE SYSTEM SHALL <response>
Example:
IF user is not authenticated
THEN THE SYSTEM SHALL redirect to login page
WHILE Pattern (Continuous)
Use for ongoing behaviors and continuous conditions.
WHILE <ongoing condition>
THE SYSTEM SHALL <continuous behavior>
Example:
WHILE file upload is in progress
THE SYSTEM SHALL display progress indicator
WHERE Pattern (Contextual)
Use for context-dependent and environmental conditions.
WHERE <context/environment>
THE SYSTEM SHALL <contextual behavior>
Example:
WHERE user has admin role
THE SYSTEM SHALL display admin controls
Compound Pattern
Combine patterns for complex requirements.
WHEN <event> AND <additional condition>
THEN THE SYSTEM SHALL <response>
Example:
WHEN user submits form AND validation passes
THEN THE SYSTEM SHALL save data and show success message
Pattern Selection Guide
| Pattern | Use When |
|---|---|
| WHEN | Event-driven behaviors, user actions |
| IF | State-based conditions, logical branching |
| WHILE | Continuous behaviors, ongoing conditions |
| WHERE | Context-dependent, environmental conditions |
Phase 2 Role
EARS is used in how.md to specify system behavior per User Story, complementing Gherkin scenarios defined in ux.md.
- ux.md (Phase 1): Gherkin scenarios define user-facing behavior (Given/When/Then)
- how.md (Phase 2): EARS statements define system-level behavior (WHEN/THE SYSTEM SHALL)
EARS statements in how.md should be testable and map to implementation requirements that the Gherkin scenarios alone do not capture (e.g., performance constraints, error handling at system level, data validation rules).