@Test
public void testRetract() throws
        Exception {

    toni.uuidKey.retract();
    Util.assertMapContent(map.get(UUIDKey.UNIQUE_UUID),
                          eder.uuidKey,
                          michael.uuidKey);
    Util.assertMapContent(map.get(KeyDefinition.newKeyDefinition()
                                          .withId("name")
                                          .build()),
                          "Eder",
                          "Michael");
    Util.assertMapContent(map.get(KeyDefinition.newKeyDefinition()
                                          .withId("age")
                                          .build()),
                          20,
                          30);
}