checkNoOutput(onChar, ITERABLE_);
    checkResult(onChar, ITERABLE_1, "1");
    checkResult(onChar, ITERABLE_12, "1-2");
    checkResult(onChar, ITERABLE_123, "1-2-3");
  }

  public void testSkipNulls() {
    Joiner skipNulls = J.skipNulls();
    checkNoOutput(skipNulls, ITERABLE_);
    checkNoOutput(skipNulls, ITERABLE_NULL);
    checkNoOutput(skipNulls, ITERABLE_NULL_NULL);