time_travel always fails when blocks is 0

[antazoey]

(Pdb) env
<boa.environment.Env object at 0x111088170>
(Pdb) env.time_travel(seconds=123, blocks=0)
*** ValueError: One of seconds or blocks should be set

Looking at the code:

if (seconds is None) == (blocks is None):

Both seconds is not None and blocks is not None and those are equal so i get the weird error message.
Workaround:

env.time_travel(seconds=123, blocks=None)

^ but kinda weird when params are dynamically figured out

[charles-cooper]

i think this is expected behavior -- time_travel only allows one of block_number or timestamp to be set. if you want to set them in a "low-level" way, just modify patch.block_number and patch.timestamp directly

[antazoey]

Ah, in that case I would suggest adjusting the error message:

ValueError: One of seconds or blocks should be set

to something like

ValueError: One (and only one) of seconds or blocks should be set

[charles-cooper]

#359