   for (const condition of options.conditions) {
      animation.currentTime = condition.currentTime;
      assert_equals(animation.effect.getComputedTiming().progress,
                    condition.progress,
                    `Progress at ${animation.currentTime}ms`);
    }
  }, options.description);
}

test(t => {
  const target = createDiv(t);
  const anim = target.animate(
      [
        { easing: 'steps(1, start)', opacity: 0 },
        { opacity: 1 }
      ],
      { easing: 'linear(-2, 2)', durati