unit-test-mapper-converter

Unit test MapStruct mappers by writing JUnit 5 tests that exercise toDto, toEntity, and toDtos methods. Verify field mappings match expected values, nested objects transform correctly, and null inputs map gracefully using assertion libraries.

Test nested address, phone, and other complex object mappings by asserting that child objects and their fields transform correctly through the mapper. Verify nested null handling and type conversions propagate as expected across DTO and domain hierarchies.

MapStruct mappers require explicit null-handling tests to ensure null inputs don't cause exceptions. Write unit tests that pass null DTOs, null entities, and null nested fields, then verify the mapper returns null or default values without errors.

Yes. Include custom converters in your JUnit 5 test suite with MapStruct mappers. Test converter logic for type conversions, field transformations, and nested structures using the same assertion patterns and null-handling coverage.

MapStruct mapper unit testing requires MapStruct library, JUnit 5 (junit-jupiter), and assertion libraries like AssertJ or Hamcrest. These enable comprehensive validation of field mappings, nested transformations, and null-safety across DTO and entity conversions.

Nested mappings introduce complexity: child objects must map correctly, null nested fields must not break the parent mapping, and type conversions must cascade through object hierarchies. Dedicated tests catch these issues that flat mappings might miss.