@Test
  public void findBestForSkill() {
    service.addRanking(r1, s1, skill, 6);
    service.addRanking(r1, s2, skill, 9); /*7,5*/

    service.addRanking(r2, s1, skill, 4);
    service.addRanking(r2, s2, skill, 2); /*3*/

    service.addRanking(r3, s1, skill, 8);
    service.addRanking(r3, s2, skill, 9);
    service.addRanking(r3, s3, skill, 9); /*8,66*/

    service.addRanking(r4, s1, skill, 9);
    service.addRanking(r4, s2, skill, 1); /*5*/

    service.addRanking(r5, s1, skill, 1); /*1*/

    service.addRanking(r5, s1, skill2, 1);

    Person p = service.findBestForSkill(skill);
    assertEquals(p.getName(), r3);
  }
 @Test
 public void findBestForNonexistingSkill() {
   Person p = service.findBestForSkill("no skill");
   assertNull(p);
 }