unit-test-utility-methods

Unit tests for static utility methods exercise pure functions directly using JUnit 5 and AssertJ assertions. Write focused tests that call static helpers with various inputs—including edge cases like null values, empty collections, and boundary conditions—to verify correctness without relying on instance state.

Pure functions benefit from exhaustive edge-case coverage: test null inputs, empty strings or collections, boundary values, and expected exceptions. Use AssertJ assertions to verify behavior across these scenarios systematically, ensuring your utility code handles all real-world inputs safely.

Yes. JUnit 5 with AssertJ is well-suited for testing string, math, collection, and formatting utility classes. AssertJ's fluent assertions make it easy to verify output correctness, compare results against expected values, and validate behavior across diverse input types and edge cases.

Static utility methods require the same rigor as instance methods but with one key difference: they're pure functions with no state to mock or manage. Focus on input validation, null safety, and comprehensive edge-case coverage using straightforward JUnit 5 tests and AssertJ assertions.

Validation utilities often guard against invalid data at application boundaries. Testing them thoroughly—covering valid inputs, invalid formats, null handling, and boundary conditions—ensures your utility code prevents downstream errors and maintains data integrity across your application.