assertEquals("backward", nullsArePassed.reverse().convert("foo"));
    assertEquals("backward", nullsArePassed.reverse().convert(null));
  }

  public void testNullIsNotPassedThrough() {
    Converter<String, String> nullsAreHandled = sillyConverter(true);
    assertEquals("forward", nullsAreHandled.convert("foo"));
    assertEquals(null, nullsAreHandled.convert(null));