positionEquals(container, 0, 300, 0, 300), "container position ok");
          assert.isTrue(positionEquals(c1, 0, 300, 0, 50), "child 1 position ok");
        });

        test('layout-center', function() {
          container.classList.add('center');
          container.classList.add('tall');
          assert.isTrue(positionEquals(container, 0, 300, 0, 300), "container position ok");
          var center = (300 - 50) / 2;
          assert.isTrue(positionEquals(c1, center, center + 50, 0, 50), "child 1 pos