• Core business features need correctness validation before release.
• Requirement changes may affect user journeys and business rules.
• Team needs confidence in end-to-end behavior under normal and abnormal inputs.

• Verify feature behavior against business requirement and acceptance criteria.
• Detect logic gaps across state transitions and exception handling.
• Deliver a clear quality picture for functional readiness.

1. Build function map from requirement and user workflow.
2. Identify main/edge/negative scenarios and decision branches.
3. Prepare representative test data and preconditions.
4. Execute and verify UI, API, and data consistency.
5. Record defects with business impact and reproducibility.
6. Summarize readiness and remaining functional risk.

Input:

• Feature: refund with partial amount and coupon rollback

Output:

• Validated normal and edge paths including rollback exceptions
• Found mismatch between UI state and settlement record

Input:

• "Test refund feature quickly"

Output (problem):

• Only one happy path checked, no state/exception coverage
• False confidence before release

• Do not reduce functional testing to superficial click-through.
• Do not skip exception and rollback paths.
• Do not validate UI only while ignoring data/state consistency.
• Do not mark pass without requirement traceability.
• Do not ignore cross-module dependency effects.