=== TEST ===
package org.flyveleder.support;

import org.junit.jupiter.api.Test;

import java.time.LocalDate;

import static org.junit.jupiter.api.Assertions.*;

class AgeTest {

    @Test
    void getAge() {

        LocalDate birthDay =LocalDate.of(1975,11,8);
        LocalDateContract ldc = new MockLocalDateProvider();
        Age age = new Age(birthDay);
        age.setLocalDateProvider(ldc);
        assertEquals(24, age.getAge());
    }

    private class MockLocalDateProvider implements LocalDateContract {

        @Override
        public LocalDate now() {
            return LocalDate.of(2000,10,10);
        }
    }
}



=== IMPL ===
package org.flyveleder.support;

import java.time.LocalDate;
import java.time.Period;

public class Age {

    private final LocalDate birthdate;
    private LocalDateContract localDateProvider = new LocalDateProvider();

    public Age(LocalDate birthdate) {
        assert birthdate != null;
        this.birthdate = birthdate;
    }

    public int getAge() {

        Period period = Period.between(birthdate, localDateProvider.now() );
        return period.getYears();
    }

    public boolean isBirthDay() {
        return birthdate.equals(localDateProvider.now());
    }

    public void setLocalDateProvider(LocalDateContract ldp) {
        localDateProvider = ldp;
    }

    private class LocalDateProvider implements LocalDateContract {

        @Override
        public LocalDate now() {
            return LocalDate.now();
        }
    }

}