unit-test-utility-methods

SKILL.md

JUnit 5 patterns for testing utility classes, static methods, and pure functions without mocking complexity.

Covers testing strategies for string manipulation, calculations, collections, data validation, and format utilities with edge case and boundary condition handling

Uses AssertJ assertions for readable test code and @ParameterizedTest for testing multiple similar scenarios efficiently

Emphasizes null handling, empty inputs, extreme values, and floating-point precision as critical edge cases

Includes best practices for pure functions, descriptive test naming, and avoiding over-mocking in utility testing

Unit Testing Utility Classes and Static Methods

Overview

This skill generates tests for utility classes with static helper methods and pure functions. It provides patterns for testing null handling, edge cases, boundary conditions, and common utilities like string manipulation, calculations, data validation, and collections. Pure functions require no mocking.

When to Use

Use this skill when:

Writing tests for utility/helper classes with static methods

Testing pure functions with no state or side effects

Testing string manipulation, formatting, or transformation utilities

Testing calculation, conversion, or math helper functions

Testing data validation and formatter utilities

Verifying null/empty input handling in utility code

Testing collections or array helper methods

Instructions