How to use the cantools.db.Database function in cantools

def test_socialledge_encode_decode_mux_0(self):
        """Encode and decode the signals in a SENSOR_SONARS frame with mux 0.

        """

        db = cantools.db.Database()
        filename = os.path.join('tests', 'files', 'socialledge.dbc')
        db.add_dbc_file(filename)

        frame_id = 200

        decoded_message = {
            'SENSOR_SONARS_mux': 0,
            'SENSOR_SONARS_err_count': 1,
            'SENSOR_SONARS_left': 2,
            'SENSOR_SONARS_middle': 3,
            'SENSOR_SONARS_right': 4,
            'SENSOR_SONARS_rear': 5
        }
        encoded_message = b'\x10\x00\x14\xe0\x01( \x03'

        encoded = db.encode_message(frame_id, decoded_message)

def test_foobar_encode_decode(self):
        db = cantools.db.Database()
        filename = os.path.join('tests', 'files', 'foobar.dbc')
        db.add_dbc_file(filename)

        messages = [
            (
                'Foo',
                {'Foo': 250, 'Bar': 0.0},
                b'\x00\x00\x00\x00\x00\x00\x00\x00'
            ),
            (
                'Fum',
                {'Fum': 9, 'Fam': 5},
                b'\x09\x50\x00\x00\x00'
            ),
            (
                'Bar',

def test_foobar_decode_masked_frame_id(self):
        db = cantools.db.Database(frame_id_mask=0xff)
        filename = os.path.join('tests', 'files', 'foobar.dbc')
        db.add_dbc_file(filename)

        frame_ids = [
            0x12331,
            0xfff31,
            0x00031
        ]

        for frame_id in frame_ids:
            db.get_message_by_frame_id(frame_id)

def test_add_bad_sym_string(self):
        db = cantools.db.Database()

        with self.assertRaises(cantools.db.ParseError) as cm:
            db.add_sym_string('FormatVersion=6.0\n'
                              'Foo="Jopp"')

        self.assertEqual(
            str(cm.exception),
            'Invalid SYM syntax at line 2, column 1: \'>!

def test_foobar_decode_masked_frame_id(self):
        db = cantools.db.Database(frame_id_mask=0xff)
        filename = os.path.join('tests', 'files', 'foobar.dbc')
        db.add_dbc_file(filename)

        frame_ids = [
            0x12331,
            0xfff31,
            0x00031
        ]

        for frame_id in frame_ids:
            db.get_message_by_frame_id(frame_id)

def test_motohawk_encode_decode(self):
        """Encode and decode the signals in a ExampleMessage frame.

        """

        db = cantools.db.Database()
        filename = os.path.join('tests', 'files', 'motohawk.dbc')
        db.add_dbc_file(filename)

        example_message_name = 'ExampleMessage'
        example_message_frame_id = 496

        # Encode with non-enumerated values.
        decoded_message = {
            'Temperature': 250.55,
            'AverageRadius': 3.2,
            'Enable': 1
        }
        encoded_message = b'\xc0\x06\xe0\x00\x00\x00\x00\x00'

        encoded = db.encode_message(example_message_frame_id, decoded_message)
        self.assertEqual(encoded, encoded_message)

def test_missing_dbc_specifics(self):
        db = cantools.db.Database()

        node = cantools.db.Node('FakeNode', 'Comment')
        db.nodes.append(node)

        signals = [cantools.db.Signal('C', 0, 8)]
        message = cantools.db.Message(0x20, 'D', 8, signals)
        db.messages.append(message)

        # Test that dump executes without raising.
        db.as_dbc_string()

def test_encode_decode_no_scaling_no_decode_choices(self):
        """Encode and decode a message without scaling the signal values, not
        decoding choices.

        """

        db = cantools.db.Database()
        filename = os.path.join('tests', 'files', 'motohawk.dbc')
        db.add_dbc_file(filename)

        decoded_message = {
            'Temperature': 3,
            'AverageRadius': 2,
            'Enable': 1
        }
        encoded_message = b'\x84\x00\x60\x00\x00\x00\x00\x00'

        encoded = db.encode_message(496,
                                    decoded_message,
                                    scaling=False)
        self.assertEqual(encoded, encoded_message)

        decoded = db.decode_message(496,

def test_jopp_6_0_sym(self):
        filename = os.path.join('tests', 'files', 'jopp-6.0.sym')
        db = cantools.db.Database()
        db.add_sym_file(filename)

        self.assertEqual(len(db.messages), 6)
        self.assertEqual(len(db.messages[0].signals), 0)

        # Message1.
        message_1 = db.messages[3]
        self.assertEqual(len(message_1.signals), 2)
        self.assertEqual(message_1.frame_id, 0)
        self.assertEqual(message_1.is_extended_frame, False)
        self.assertEqual(message_1.name, 'Message1')
        self.assertEqual(message_1.length, 8)
        self.assertEqual(message_1.senders, [])
        self.assertEqual(message_1.send_type, None)
        self.assertEqual(message_1.cycle_time, 30)
        self.assertEqual(len(message_1.signals), 2)

def test_the_homer_float(self):
        filename = os.path.join('tests', 'files', 'the_homer.kcd')
        db = cantools.db.Database()
        db.add_kcd_file(filename)

        # Message 1 (binary64).
        frame_id = 0x832

        decoded_message = {'AmbientLux': math.pi}
        encoded_message = b'\x18\x2d\x44\x54\xfb\x21\x09\x40'

        encoded = db.encode_message(frame_id, decoded_message)
        self.assertEqual(len(encoded), 8)
        self.assertEqual(encoded, encoded_message)
        decoded = db.decode_message(frame_id, encoded)
        self.assertEqual(decoded, decoded_message)

        # Message 2 (binary32).
        frame_id = 0x845