Phase 3: Property-Based Testing for AI Code · 55 min · Python · Hypothesis · pytest

Deriving Properties from Code

Read the code. Find the invariants. Write the properties.

Real-world application: Engineers who can derive properties (roundtrip, monotonicity, bounded output, commutativity, identity) from code demonstrate the analytical skills needed to specify invariants for AI-generated functions.

What you will learn

Derive roundtrip properties from serialization/deserialization functions
Derive monotonicity properties from sorting and comparison functions
Derive bounded output properties from mathematical functions
Derive commutativity and identity properties from binary operations
Use the Roundtrip/Model-oracle/Invariant property taxonomy

Introduction

Deriving Properties from Code

Objective

Run the property derivation framework on 3 AI-generated functions (normalize, encode/decode, sort) and observe which property types catch bugs in each function.

Read the code. Find the invariants. Write the properties.

Unlock the full lesson

You've read the first 2 sections. The rest of this lesson covers The Problem, The Concept, Build, Check Yourself, Key Terms & Next — plus a hands-on lab, quiz, and project artifact.

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