Clockabilly

A really simple trait wrapper for chrono that lets you mock out time in tests.

Usage

Any place you want to mock time, you need to pass in a Clockable interface. In your "real" code you can use a UtcClock, and in your testing code you can use a MockUtcClock (you need to include the mock feature for this). See the basic example for an example:

> cargo run --example basic --features=mock
   Compiling clockabilly v0.0.0 (/build/src/clockabilly)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.09s
     Running `target/debug/examples/basic`
2024-07-17T17:41:02.369894602Z
1970-01-01T00:00:10Z

For "simplicity", this re-exports all of chrono.

Sleeping

You can also use this in place of calls to tokio::time::sleep; the real clock is just a wrapper around sleep, and the fake clock just advances the internal time counter by however many seconds you slept for.

Callbacks

You can provide callback functions that change external state using the add_callbacks function, e.g.,

let mut x = 10;
let mut clock = MockUtcClock::new(0);
clock.add_callback(1, || x += 5); // Probably doesn't actually compile, because you probably need Arcs and stuff
clock.sleep(20);
assert_eq!(15, x);

You can add multiple callbacks for each timestamp; callbacks for a particular timestamp are executed in the order they were added. Note that sleep and advance both execute the callbacks, but set does not.