scratch-vm/test/unit/util_timer.js

const test = require('tap').test;
const Timer = require('../../src/util/timer');

// Stubbed current time
let NOW = 0;

const testNow = {
    now: () => {
        NOW += 100;
        return NOW;
    }
};

test('spec', t => {
    const timer = new Timer(testNow);

    t.type(Timer, 'function');
    t.type(timer, 'object');

    t.type(timer.startTime, 'number');
    t.type(timer.time, 'function');
    t.type(timer.start, 'function');
    t.type(timer.timeElapsed, 'function');
    t.type(timer.setTimeout, 'function');
    t.type(timer.clearTimeout, 'function');

    t.end();
});

test('time', t => {
    const timer = new Timer(testNow);
    const time = timer.time();

    t.ok(testNow.now() >= time);
    t.end();
});

test('start / timeElapsed', t => {
    const timer = new Timer(testNow);
    const delay = 100;
    const threshold = 1000 / 60; // 60 hz

    // Start timer
    timer.start();

    // Measure timer
    const timeElapsed = timer.timeElapsed();
    t.ok(timeElapsed >= 0);
    t.ok(timeElapsed >= (delay - threshold) &&
         timeElapsed <= (delay + threshold));
    t.end();
});

test('setTimeout / clearTimeout', t => new Promise((resolve, reject) => {
    const timer = new Timer(testNow);
    const cancelId = timer.setTimeout(() => {
        reject(new Error('Canceled task ran'));
    }, 1);
    timer.setTimeout(() => {
        resolve('Non-canceled task ran');
        t.end();
    }, 2);
    timer.clearTimeout(cancelId);
}));