Instancio

// Inject a random Person using @Given
@ExtendWith(InstancioExtension.class)
class PersonMapperTest {

    @Test
    void shouldMapToDto(@Given Person person) {
        PersonDto dto = PersonMapper.toDto(person);
        assertThat(dto.getName()).isEqualTo(person.getName());
        assertThat(dto.getEmail()).isEqualTo(person.getEmail());
    }
}
// Or create manually with overrides
Person person = Instancio.of(Person.class)
    .set(field(Person::getName), "Alice")
    .generate(field(Person::getAge),
        gen -> gen.ints().range(18, 65))
    .create();