Test data contains invalid messages, but should not

Have a look at

logformats_test

def test_can_error_frame_ext(self):
expected = can.Message(
timestamp=2459565876.494607,
is_error_frame=True,
arbitration_id=0x19999999,
is_extended_id=True,
channel=0x1110,
**dlc=0x66**,
data=[0xCC, 0xDD, 0xEE, 0xFF, 0x11, 0x22, 0x33, 0x44],
)
actual = self._read_log_file("test_CanErrorFrameExt.blf")
self.assertMessagesEqual(actual, [expected] * 2)
self.assertEqual(actual[0].channel, expected.channel)

Even with an FD frame and treading dlc as length, this an invalid message. But code seems not to expect an invalid message.