NullPointerTester tester =
        new NullPointerTester().setDefault(String.class, "HmacMD5").setDefault(Key.class, MD5_KEY);
    tester.testAllPublicConstructors(MacHashFunction.class);
    tester.testAllPublicInstanceMethods(new MacHashFunction("HmacMD5", MD5_KEY, "toString"));
  }

  public void testHashing() throws Exception {
    for (String stringToTest : INPUTS) {

   * @param key the secret key
   * @throws IllegalArgumentException if the given key is inappropriate for initializing this MAC
   * @since 20.0
   */
  public static HashFunction hmacMd5(Key key) {
    return new MacHashFunction("HmacMD5", key, hmacToString("hmacMd5", key));
  }

  /**
   * Returns a hash function implementing the Message Authentication Code (MAC) algorithm, using the