@Override
  @Test
  public void forEachKey() {
    super.forEachKey();

    final UnifiedSet<String> set = UnifiedSet.newSet(5);

    // map with a chain and empty slots
    MutableMap<Integer, Integer> map = this.mapWithCollisionsOfSize(5);
    map.forEachKey(
        new Procedure<Integer>() {
          public void value(Integer each) {
            set.add(each.toString());
          }
        });
    Assert.assertEquals(UnifiedSet.newSetWith("0", "17", "34", "51", "68"), set);
  }