public virtual void zipWithIndex()
{
Stream <string> letters = Stream.of("a", "b", "c");
IDictionary <int, string> expected = ImmutableMap.of(0, "a", 1, "b", 2, "c");
IDictionary <int, string> result = MapStream.zipWithIndex(letters).toMap();
assertThat(result).isEqualTo(expected);
}