assertThrows(NumberFormatException.class, () -> UnsignedLongs.parseUnsignedLong("0", -1));
  }

  public void testToString() {
    String[] tests = {
      "0",
      "ffffffffffffffff",
      "7fffffffffffffff",
      "ff1a618b7f65ea12",
      "5a4316b8c153ac4d",
      "6cf78a4b139a4e2a"
    };
    int[] bases = {2, 5, 7, 8, 10, 16};
    for (int base : bases) {
      for (String x : tests) {

        // Test various long values
        assertEquals("0000000000000000", Hexdump.toHexString(0L, 16));
        assertEquals("00000000000000FF", Hexdump.toHexString(255L, 16));
        assertEquals("FFFFFFFFFFFFFFFF", Hexdump.toHexString(-1L, 16));

        // Test different sizes
        assertEquals("00000000", Hexdump.toHexString(0L, 8));
        assertEquals("12345678", Hexdump.toHexString(0x12345678L, 8));
    }

    } else if (frameLength == PAYLOAD_LONG.toLong()) {
      frameLength = source.readLong()
      if (frameLength < 0L) {
        throw ProtocolException(
          "Frame length 0x${frameLength.toHexString()} > 0x7FFFFFFFFFFFFFFF",
        )
      }
    }

    if (isControlFrame && frameLength > PAYLOAD_BYTE_MAX) {
      throw ProtocolException("Control frame must be less than ${PAYLOAD_BYTE_MAX}B.")
    }

        assertEquals("12345678", Hexdump.toHexString(0x12345678L, 8));
        assertEquals("5678", Hexdump.toHexString(0x12345678L, 4));

        // Test negative values (treated as unsigned)
        assertEquals("FFFFFFFFFFFFFFFF", Hexdump.toHexString(-1L, 16));
        assertEquals("FFFFFFFF", Hexdump.toHexString(-1L, 8));
        assertEquals("FFFF", Hexdump.toHexString(-1L, 4));
    }

    @Test

    assertFailsWith<ProtocolException> {
      clientReader.processNextFrame()
    }.also { expected ->
      assertThat(expected.message).isEqualTo(
        "Frame length 0x8000000000000000 > 0x7FFFFFFFFFFFFFFF",
      )
    }
  }

  @Test fun serverHelloTwoChunks() {
    data.write("818537fa213d7f9f4d".decodeHex()) // Hel
    data.write("5158".decodeHex()) // lo
    serverReader.processNextFrame()