assertThat(base16().upperCase()).isSameInstanceAs(base16());
  }

  public void testBase16LowerCase() {
    BaseEncoding lowerCase = base16().lowerCase();
    assertThat(lowerCase).isNotSameInstanceAs(base16());
    assertThat(lowerCase).isSameInstanceAs(base16().lowerCase());
    testEncodingWithCasing(lowerCase, "foobar", "666f6f626172");
  }

  public void testBase16IgnoreCase() {
    BaseEncoding ignoreCase = base16().ignoreCase();

  }

  /**
   * If the argument is a {@linkplain #isLowerCase(char) lowercase ASCII character}, returns the
   * uppercase equivalent. Otherwise returns the argument.
   */
  public static char toUpperCase(char c) {
    return isLowerCase(c) ? (char) (c ^ CASE_MASK) : c;
  }

  /**
   * Indicates whether {@code c} is one of the twenty-six lowercase ASCII alphabetic characters

    assertThat(base16().upperCase()).isSameInstanceAs(base16());
  }

  public void testBase16LowerCase() {
    BaseEncoding lowerCase = base16().lowerCase();
    assertThat(lowerCase).isNotSameInstanceAs(base16());
    assertThat(lowerCase).isSameInstanceAs(base16().lowerCase());
    testEncodingWithCasing(lowerCase, "foobar", "666f6f626172");
  }

  public void testBase16IgnoreCase() {
    BaseEncoding ignoreCase = base16().ignoreCase();

  private static final String UPPER = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

  public void testToLowerCase() {
    assertEquals(LOWER, Ascii.toLowerCase(UPPER));
    assertSame(LOWER, Ascii.toLowerCase(LOWER));
    assertEquals(IGNORED, Ascii.toLowerCase(IGNORED));
    assertEquals("foobar", Ascii.toLowerCase("fOobaR"));
  }

  public void testToUpperCase() {
    assertEquals(UPPER, Ascii.toUpperCase(LOWER));

    }

    Alphabet lowerCase() {
      if (!hasUpperCase()) {
        return this;
      }
      checkState(!hasLowerCase(), "Cannot call lowerCase() on a mixed-case alphabet");
      char[] lowerCased = new char[chars.length];
      for (int i = 0; i < chars.length; i++) {
        lowerCased[i] = Ascii.toLowerCase(chars[i]);
      }
      Alphabet lowerCase = new Alphabet(name + ".lowerCase()", lowerCased);

  }

  /**
   * If the argument is a {@linkplain #isLowerCase(char) lowercase ASCII character}, returns the
   * uppercase equivalent. Otherwise returns the argument.
   */
  public static char toUpperCase(char c) {
    return isLowerCase(c) ? (char) (c ^ CASE_MASK) : c;
  }

  /**
   * Indicates whether {@code c} is one of the twenty-six lowercase ASCII alphabetic characters

  private static final String UPPER = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

  public void testToLowerCase() {
    assertEquals(LOWER, Ascii.toLowerCase(UPPER));
    assertSame(LOWER, Ascii.toLowerCase(LOWER));
    assertEquals(IGNORED, Ascii.toLowerCase(IGNORED));
    assertEquals("foobar", Ascii.toLowerCase("fOobaR"));
  }

  public void testToUpperCase() {
    assertEquals(UPPER, Ascii.toUpperCase(LOWER));

  }

  public void testToString() {
    byte[] data = new byte[] {127, -128, 5, -1, 14};
    assertEquals("7f8005ff0e", HashCode.fromBytes(data).toString());
    assertEquals("7f8005ff0e", base16().lowerCase().encode(data));
  }

  public void testHashCode_nulls() throws Exception {
    sanityTester().testNulls();
  }

  public void testHashCode_equalsAndSerializable() throws Exception {

    byte[] data = fillByteArray(50, 0xdd);

    checkSha1("125d7342b9ac11cd91a39af48aa17b4f63f175d3", key, data);
  }

  public void testRfc2202_hmacSha1_case4() {
    byte[] key = base16().lowerCase().decode("0102030405060708090a0b0c0d0e0f10111213141516171819");
    byte[] data = fillByteArray(50, 0xcd);

    checkSha1("4c9007f4026250c6bc8414f9bf50c86c2d7235da", key, data);
  }

    byte[] data = fillByteArray(50, 0xdd);

    checkSha1("125d7342b9ac11cd91a39af48aa17b4f63f175d3", key, data);
  }

  public void testRfc2202_hmacSha1_case4() {
    byte[] key = base16().lowerCase().decode("0102030405060708090a0b0c0d0e0f10111213141516171819");
    byte[] data = fillByteArray(50, 0xcd);

    checkSha1("4c9007f4026250c6bc8414f9bf50c86c2d7235da", key, data);
  }