import {FpsCounter} from './fps-counter';

describe('FpsCounter', () => {
  const FRAME_MS = 1000 / 60;

  it('publishes 60 after the first 500 ms window and not before', () => {
    const counter = new FpsCounter();
    const at = (frame: number) => 1 + FRAME_MS * frame;

    for (let frame = 0; at(frame) - 1 < 500; frame++) {
      counter.tick(at(frame));
    }
    expect(counter.fps()).toBe(0);

    counter.tick(at(30)); // 30 ticks since the window opened, 500 ms elapsed
    expect(counter.fps()).toBe(60);
  });

  it('reset sets the rate back to 0', () => {
    const counter = new FpsCounter();
    for (let i = 0; i <= 61; i++) {
      counter.tick(1 + FRAME_MS * i);
    }
    expect(counter.fps()).toBeGreaterThan(0);

    counter.reset();

    expect(counter.fps()).toBe(0);
  });
});