change, increase, decrease matchers

[hieueastagile]

Use case

Example, we have a function

def decrease_it(a):
  return a - 1

We might want to test it, and here's a few possible matchers that we might want to use

expect(decrease_it).to.change(a).from(2).to(1)
expect(decrease_it).to.decrease(a).by(1)
expect(decrease_it).to.increase(a).by(-1)

[hieueastagile]

We might need to resolve this first: https://github.com/EastAgile/robber.py/issues/4

[catriuspham]

I see that we aldready have the chain expect(func).to.change(arg).by(arg). Do we still need these change.from.to, decrease, increase chains?

[hieueastagile]

from... to doesn't work, actually, since from is python keywords, that's why @hotay use change... by instead.

[catriuspham]

How about decrease and increase then? Do we still need to implement them?

[hieueastagile]

We should do.

[catriuspham]

@hieueastagile our current change.by is the same as your suggested increase.by do you want to keep both or just one of them?

[hieueastagile]

@catriuspham Looking into it again. I think we should close this issue, change.by is good enough and it should be the only obvious way for this, we don't need to introduce more ways, it seems to break the Python Zen here.