@Test
public void testOfToString() {

  BigInteger modulus = new BigInteger("13");
  Assert.assertThat(
      new BigIntegerModulus(modulus).toString(),
      Matchers.containsString(modulus.toString()));
  Assert.assertThat(
      new BigIntegerModulus(modulus).toString(),
      Matchers.containsString("BigIntegerModulus"));
}