Assert — Assertion Patterns Reference

---

name: "assert"

version: "1.0.0"

description: "Assertion patterns reference — guard clauses, preconditions, invariants, and contract programming. Use when writing defensive code, validating inputs, or implementing design-by-contract."

author: "BytesAgain"

homepage: "https://bytesagain.com"

source: "https://github.com/bytesagain/ai-skills"

tags: [assert, assertion, precondition, invariant, contract, defensive, testing]

category: "devtools"

---

# Assert — Assertion Patterns Reference

Quick-reference skill for assertion techniques, design-by-contract, and defensive programming patterns.

When to Use

Commands

`intro`

scripts/script.sh intro

Overview of assertions — purpose, philosophy, and when to use them vs exceptions.

`preconditions`

scripts/script.sh preconditions

Precondition patterns: validating inputs, guard clauses, and fail-fast design.

`postconditions`

scripts/script.sh postconditions

Postcondition patterns: validating outputs and return value contracts.

`invariants`

scripts/script.sh invariants

Class and loop invariants — maintaining consistent state throughout execution.

`languages`

scripts/script.sh languages

Assertion syntax and behavior in Python, Java, C, JavaScript, Rust, Go.

`contracts`

scripts/script.sh contracts

Design-by-contract methodology — Bertrand Meyer's approach and modern implementations.

`antipatterns`

scripts/script.sh antipatterns

Common assertion mistakes: side effects, catching AssertionError, using in production flow.

`strategies`

scripts/script.sh strategies

Assertion strategies for different contexts: unit tests, production code, APIs, libraries.

`help`

scripts/script.sh help

`version`

scripts/script.sh version

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