unit-test-utility-methods

# 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 1. **Create test class**: Name it after the utility (e.g., `StringUtilsTest`) 2. **Test happy path**: Valid inputs with expected outputs 3. **Test edge cases**: null, empty, whitespace, single elements 4. **Test boundary conditions**: max/min values, large numbers, precision 5. **Use descriptive names**: `shouldCapitalizeFirstLetter` instead of `test1` 6. **Use AssertJ**: For readable, chainable assertions 7. **Use `@ParameterizedTest`**: For multiple similar inputs (see `references/parameterized-tests.md`) 8. **Avoid mocking**: Pure utilities need no mocks ## Examples ### Basic Static Utility Test ```java import org.junit.jupiter.api.Test; import static org.assert...