Add shift() method

[alex-verve]

refs #20

[adamchainz]

Thanks !

[adamchainz]

So I'm thinking this through a bit. I am not sure if it's wise to pursue 100% the same API as freezegun here because it's a bit confusing.

The name tick has two distinct meanings. The tick argument to travel() 'makes sense' to me - it "keeps the clock ticking." The tick() method - well it offsets the current time, even in reverse.

I'm also not sold on the default being 1 second. When is that useful case? Wouldn't it better to be explicit, for the sake of writing '1' in tests to make it clear how much time is moving by?

I'm gonna mull this over for a little bit, it's especially a question as to whether I want this library to have the exact same API as freezegun, or just to support the same use cases. There's some support for copying the core technique over to freezegun so I might be free-er to use a different API here.

[alex-verve]

The tick() method - well it offsets the current time, even in reverse.

Totally agree, it is confusing to have two different things called tick.
I think that idea of having different API is wise in that case (as long as time-machine has covered all use cases).

What do you think of these?

def test_coordinates_add_timedelta():
    with time_machine.travel(EPOCH, tick=False) as coordinates:
        coordinates += dt.timedelta(seconds=1)

        assert time.time() == EPOCH + 1


def test_coordinates_set_exact_time():
    destination_dt = dt.datetime(2000, 1, 1)

    with time_machine.travel(EPOCH, tick=False) as traveller:
        traveller.move_to(destination_dt)

        # or maybe even? :)
        traveller >> destination_dt

        assert time.time() == destination_dt.timestamp()

[adamchainz]

I don't like operator overloading, it is a bit implicit. Perhaps shift()? Or move_offset() ?

[alex-verve]

I like both shift() and move_offset() 😃
Did you consider having one method for both things: move(offset=..)/move(to=..)? (not sure if it's good idea tho).
Maybe we need to hear opinion from thee wider public?

[adamchainz]

I've gone with shift() as you've seen. I think it's a good name, better than tick(). If anyone finds a problem with it, we can always add an alias.