@Test
public void putReturnsOldValueForNewAssociation() {

    final String permission = "READ";
    final Map<String, Integer> weightedSubjectId = Collections.singletonMap(subjectId, 0);
    underTest.put(permission, weightedSubjectId);
    final Map<String, Integer> oldValue = underTest.put(permission, Collections.singletonMap(subjectId, 1));
    assertThat(oldValue).isEqualTo(weightedSubjectId);
}