Iterator<String> mod = Lists.newArrayList("a", "b", "c").iterator();
    UnmodifiableIterator<String> unmod = Iterators.unmodifiableIterator(mod);
    assertThat(unmod).isNotSameInstanceAs(mod);
    assertThat(Iterators.unmodifiableIterator(unmod)).isSameInstanceAs(unmod);
    assertThat(Iterators.unmodifiableIterator((Iterator<String>) unmod)).isSameInstanceAs(unmod);
  }

    Iterator<String> mod = Lists.newArrayList("a", "b", "c").iterator();
    UnmodifiableIterator<String> unmod = Iterators.unmodifiableIterator(mod);
    assertThat(unmod).isNotSameInstanceAs(mod);
    assertThat(Iterators.unmodifiableIterator(unmod)).isSameInstanceAs(unmod);
    assertThat(Iterators.unmodifiableIterator((Iterator<String>) unmod)).isSameInstanceAs(unmod);
  }

    EnumMap<SomeEnum, Integer> original = Maps.newEnumMap(SomeEnum.class);
    EnumMap<SomeEnum, Integer> copy = Maps.newEnumMap(original);
    assertEquals(original, copy);
    assertThat(copy).isNotSameInstanceAs(original);
  }

  public void testEnumMapWithInitialMap() {
    HashMap<SomeEnum, Integer> original = new HashMap<>();
    original.put(SomeEnum.SOME_INSTANCE, 0);