@Test
  public void testBigIntConversion() {
    BigInteger bigInteger = BigInteger.valueOf(0x1ABCDEF0123456L);
    UnsignedInt128 uInt128 = new UnsignedInt128(bigInteger);
    assertEquals(bigInteger, uInt128.toBigIntegerSlow());
  }
Testcases for {@link UnsignedInt128}

This code was based on code from Microsoft's PolyBase.
common/src/test/org/apache/hadoop/hive/common/type/TestUnsignedInt128.java