HashTestUtils.checkNo2BitCharacteristics(Hashing.md5());
    HashTestUtils.checkNoFunnels(Hashing.md5());
    HashTestUtils.assertInvariants(Hashing.md5());
    assertEquals("Hashing.md5()", Hashing.md5().toString());
  }

  public void testSha1() {
    HashTestUtils.checkAvalanche(Hashing.sha1(), 100, 0.4);
    HashTestUtils.checkNo2BitCharacteristics(Hashing.sha1());

   * <p>There is more general code provided by Bob Jenkins to test arbitrarily sized characteristics
   * using the magic of gaussian elimination: http://burtleburtle.net/bob/crypto/findingc.html.
   */
  static void checkNo2BitCharacteristics(HashFunction function) {
    Random rand = new Random(0);
    int keyBits = 32;

    // get every one of (keyBits choose 2) deltas:
    for (int i = 0; i < keyBits; i++) {