bigben

🕰️ A clock abstraction, with time travel.

Installation

gleam add bigben

Usage

import bigben/clock.{type Clock}
import bigben/fake_clock
import birl
import birl/duration
import gleam/io

pub fn main() {
 // In your production code, you'll use the real `Clock` to get the time
 // from the system:
 let clock = clock.new()
 what_day_is_it(clock) // Today is Monday.

 // In test code you can construct a `FakeClock`:
 let assert Ok(now) = birl.parse("2024-04-08T02:26:31.464Z")
 let fake_clock = fake_clock.new_at(now)
 // and pass it off as a real `Clock`:
 let clock = clock.from_fake(fake_clock)

 what_day_is_it(clock) // Today is Monday.

 // We can then manipulate the clock to help us in our tests:
 fake_clock.advance(fake_clock, duration.days(4))

 what_day_is_it(clock) // Today is Friday.
}

fn what_day_is_it(clock: Clock) {
 let day_of_the_week =
   clock
   |> clock.now
   |> birl.string_weekday

 io.println("Today is " <> day_of_the_week <> ".")
}

Targets

bigben supports the Erlang target.