Assert

---

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

Writing precondition checks for function inputs

Implementing class invariants and postconditions

Choosing between assertions and exceptions

Applying design-by-contract methodology

Understanding assertion behavior across languages

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

---

*Powered by BytesAgain | bytesagain.com | hello@bytesagain.com*