@Test
public void testSpan() throws Exception {

  RingRange r0To20 = new RingRange(BigInteger.valueOf(0L), BigInteger.valueOf(20L));
  BigInteger ringSize200 = BigInteger.valueOf(200L);
  assertEquals(20, r0To20.span(ringSize200).intValue());
  RingRange r20To0 = new RingRange(BigInteger.valueOf(20L), BigInteger.valueOf(0L));
  assertEquals(180, r20To0.span(ringSize200).intValue());
}