zontally');
          assert.closeTo(rect.top - (window.innerHeight - rect.bottom), 0, 5, 'centered vertically');
        });

        test('sized, scrolling element is constrained to viewport height', function() {
          var el = fixture('sized-x');
          el.classList.add('with-margin');
          makeScrolling(el);
          el.refit();
          var rect = el.getBoundingClientRect();
          assert.isTrue(rect.height <= window.innerHeight - 20 * 2, 'height is less than or equal to viewport heigh