clock.jump(time)

Advance the clock by jumping forward in time, firing callbacks at most once. time takes the same formats as clock.tick.

This can be used to simulate the JS engine (such as a browser) being put to sleep and resumed later, skipping intermediary timers.

import t from "tap";
import sinon from "sinon";

t.test("clock.jump ignores timers not within the jump window", (t) => {
  const clock = sinon.useFakeTimers({ now: 0 });

  let called = false;
  setTimeout(() => {
    called = true;
  }, 1000);

  clock.jump(500);

  t.notOk(called, "timer beyond jump window should not have fired");

  clock.restore();
  t.end();
});

t.test("clock.jump fires timers within the jump window at the destination time", (t) => {
  const clock = sinon.useFakeTimers({ now: 0 });

  let calledAt = null;
  setTimeout(() => {
    calledAt = Date.now();
  }, 1000);

  clock.jump(2000);

  t.equal(calledAt, 2000, "timer should fire and see the jump destination as the current time");

  clock.restore();
  t.end();
});

t.test(
  "clock.jump fires each interval at most once regardless of elapsed time",
  (t) => {
    const clock = sinon.useFakeTimers({ now: 0 });

    let callCount = 0;
    setInterval(() => {
      callCount++;
    }, 100);

    // A plain tick(1500) would fire the interval ~15 times; jump fires it once
    clock.jump(1500);

    t.equal(callCount, 1, "interval should have fired at most once");

    clock.restore();
    t.end();
  }
);

t.test("clock.jump supports human-readable string time arguments", (t) => {
  const clock = sinon.useFakeTimers({ now: 0 });

  let called = false;
  setTimeout(() => {
    called = true;
  }, 100000); // 1 minute 40 seconds

  clock.jump("01:50"); // 1 minute 50 seconds

  t.ok(called, "timer should have fired after string-format jump");

  clock.restore();
  t.end();
});