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

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