LEARN // REQUIREMENTS
L4 — Unit / Verification-Level Requirement
Lowest atomic statement, verified by a single test or proof.
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◤ ◤ DEFINITION
What it is
L4 decomposes L3 into the smallest verifiable claims — typically one assertion per requirement. Some programs stop at L3; safety-critical programs (DO-178C, ISO 26262) routinely go to L4 or further.
◤ ◤ PURPOSE
Why it exists
Provides a 1:1 mapping between a requirement and a test case, enabling objective coverage metrics and certification evidence.
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