new Builder<String, Integer>().putAll(toPut).putAll(moreToPut).buildOrThrow();
    assertMapEquals(map, "one", 1, "two", 2, "three", 3, "four", 4, "five", 5);
  }

  public void testBuilderReuse() {
    Builder<String, Integer> builder = new Builder<>();
    ImmutableMap<String, Integer> mapOne = builder.put("one", 1).put("two", 2).buildOrThrow();