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

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

preconditions

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

postconditions

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Postcondition patterns: validating outputs and return value contracts.

invariants

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Class and loop invariants — maintaining consistent state throughout execution.

languages

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

contracts

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

antipatterns

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

strategies

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

help

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version

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