def test_add_var_bytes(self):
        w = Writer()
        w.add_var_bytes(b'test', 3)

        self.assertEqual(bytearray(
            b'\x00\x00\x04'
            b'test'),
            w.bytes)

    def extData(self):
        """Serialise the extension."""
        if self.renegotiated_connection is None:
            return bytearray(0)

        writer = Writer()
        writer.addVarSeq(self.renegotiated_connection, 1, 1)
        return writer.bytes

    def test_add_five_twice(self):
        w = Writer()
        w.add(0x0102030405, 5)
        w.add(0x1112131415, 5)

        self.assertEqual(bytearray(b'\x01\x02\x03\x04\x05'
                                   b'\x11\x12\x13\x14\x15'),
                         w.bytes)

    def test_addVarSeq(self):
        w = Writer()
        w.addVarSeq([16, 17, 18], 2, 2)

        self.assertEqual(bytearray(
            b'\x00\x06' +
            b'\x00\x10' +
            b'\x00\x11' +
            b'\x00\x12'), w.bytes)

    def test_addVarSeq_triple_byte_data(self):
        w = Writer()
        w.addVarSeq([0xaa, 0xbb, 0xcc], 3, 2)

        self.assertEqual(bytearray(
            b'\x00\x09' +
            b'\x00\x00\xaa' +
            b'\x00\x00\xbb' +
            b'\x00\x00\xcc'), w.bytes)

    def test_addVarTupleSeq(self):
        w = Writer()
        w.addVarTupleSeq([(1, 2), (2, 9)], 1, 2)

        self.assertEqual(bytearray(
            b'\x00\x04' + # length
            b'\x01\x02' + # first tuple
            b'\x02\x09'   # second tuple
            ), w.bytes)

    def test_addVarTupleSeq_with_single_element_tuples(self):
        w = Writer()
        w.addVarTupleSeq([[1], [9], [12]], 2, 3)

        self.assertEqual(bytearray(
            b'\x00\x00\x06' + # length
            b'\x00\x01' + # 1st element
            b'\x00\x09' + # 2nd element
            b'\x00\x0c'), w.bytes)

 def post_write(writer, self=msg, size=size, pad_byte=pad_byte, pad=pad):
     """Monkey patch for the postWrite of handshake messages"""
     if pad is not None:
         size = len(pad)
     header_writer = Writer()
     header_writer.add(self.handshakeType, 1)
     header_writer.add(len(writer.bytes) + size, 3)
     if pad is not None:
         return header_writer.bytes + writer.bytes + pad
     elif size < 0:
         return header_writer.bytes + writer.bytes[:size]
     else:
         return header_writer.bytes + writer.bytes + \
                bytearray([pad_byte]*size)

    def test_add(self):
        w = Writer()
        w.add(255, 1)

        self.assertEqual(bytearray(b'\xff'), w.bytes)

    def test_add_with_multibyte_field(self):
        w = Writer()
        w.add(32, 2)

        self.assertEqual(bytearray(b'\x00\x20'), w.bytes)

    def test_bytes(self):
        w = Writer()
        w.bytes += bytearray(b'\xbe\xef')
        w.add(15, 1)

        self.assertEqual(bytearray(b'\xbe\xef\x0f'), w.bytes)

    def test_addVarSeq_with_three_byte_overflowing_data(self):
        w = Writer()

        with self.assertRaises(ValueError):
            w.addVarSeq([16, 17, 0x1000000], 3, 2)

    def test_add_with_five_bytes_data(self):
        w = Writer()
        w.add(0x02, 5)

        self.assertEqual(bytearray(b'\x00\x00\x00\x00\x02'), w.bytes)

    def test_addVarSeq(self):
        w = Writer()
        w.addVarSeq([16, 17, 18], 2, 2)

        self.assertEqual(bytearray(b"\x00\x06" + b"\x00\x10" + b"\x00\x11" + b"\x00\x12"), w.bytes)

 def test_addVarTupleSeq_with_double_byte_invalid_sized_tuples(self):
     w = Writer()
     with self.assertRaises(ValueError):
         w.addVarTupleSeq([(1, 2), (2, 3, 4)], 2, 2)

    def test_addFixSeq(self):
        w = Writer()
        w.addFixSeq([16,17,18], 2)

        self.assertEqual(bytearray(b'\x00\x10\x00\x11\x00\x12'), w.bytes)

    def test_add_with_underflowing_data(self):
        w = Writer()

        with self.assertRaises(ValueError):
            w.add(-1, 1)

    def test_add_with_four_bytes_overflowing_data(self):
        w = Writer()

        with self.assertRaises(ValueError):
            w.add(0x0100000000, 4)

    def test_add_with_five_underflowing_bytes(self):
        w = Writer()

        with self.assertRaises(ValueError):
            w.add(-1, 5)

    def test_add_with_five_overflowing_bytes(self):
        w = Writer()

        with self.assertRaises(ValueError):
            w.add(0x010000000000, 5)