This skill should be used when the user asks about "EARS syntax", "EARS notation", "acceptance criteria format", "SHALL patterns", "formal requirements", "WHEN THE SHALL", or needs guidance on writing testable requirements using EARS (Easy Approach to Requirements Syntax).
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examples/good-requirements.mdreferences/patterns.mdEARS (Easy Approach to Requirements Syntax) is a formal notation for writing unambiguous, testable acceptance criteria.
Every acceptance criterion follows a strict pattern with uppercase keywords. The keyword SHALL is mandatory - never use "should", "must", "will", "can", or "may".
THE [System] SHALL [behavior]
Use for requirements that are always active, with no preconditions.
Example: THE System SHALL encrypt all passwords using bcrypt
WHEN [event] THE [System] SHALL [response]
Use when a specific trigger causes behavior.
Example: WHEN a user submits the login form THE System SHALL validate credentials
WHILE [state] THE [System] SHALL [behavior]
Use for behavior that continues as long as a condition is true.
Example: WHILE the user is authenticated THE System SHALL display the dashboard
WHERE [feature is present] THE [System] SHALL [behavior]
Use for behavior dependent on a feature flag or configuration.
Example: WHERE two-factor authentication is enabled THE System SHALL require a verification code
IF [condition] THEN THE [System] SHALL [response]
Use for error cases, edge cases, and exception handling.
Example: IF the password is incorrect THEN THE System SHALL display an error message
WHILE [state] WHEN [event] THE [System] SHALL [response]
Use when both a state and an event trigger behavior.
Example: WHILE the cart is not empty WHEN the user clicks checkout THE System SHALL navigate to payment
| Scenario | Pattern | Keywords |
|---|---|---|
| Always happens | Ubiquitous | THE...SHALL |
| User action triggers | Event-Driven | WHEN...THE...SHALL |
| During a state | State-Driven | WHILE...THE...SHALL |
| Feature-dependent | Optional | WHERE...THE...SHALL |
| Error/edge case | Error Handling | IF...THEN THE...SHALL |
| State + action | Complex | WHILE...WHEN...THE...SHALL |
| Wrong | Right |
|---|---|
| "The system should..." | "THE System SHALL..." |
| "When clicking..." | "WHEN the user clicks... THE System SHALL..." |
| "Must validate..." | "THE System SHALL validate..." |
| "Handle errors appropriately" | "IF validation fails THEN THE System SHALL display..." |
For detailed patterns and examples:
references/patterns.md - Comprehensive pattern documentation with edge casesexamples/good-requirements.md - Complete example requirements documentTo validate EARS syntax, use the ears-validator script:
node scripts/ears-validator.js .specs/<feature>/requirements.md