Before/After Verification Skill

Overview

Before/after verification is a technique for proving that a stage actually changed system behavior. Instead of just checking that the final state is valid, you capture what was true BEFORE implementation and what should be true AFTER implementation. The pair proves your stage caused the change.

This matters because without before/after thinking, you can't distinguish:

• "The feature already worked" from "My stage made it work"
• "The bug was already fixed" from "My fix resolved it"
• "The endpoint existed" from "I created the endpoint"

The Delta-Proof Concept

A delta-proof is verification that proves a state transition occurred.

The Pattern