0, 0, 120), "container position ok");
          var center = (300 - 50) / 2;
          assert.isTrue(positionEquals(c1, 0, 50, 0, 50), "child 1 position ok");
          assert.isTrue(positionEquals(c2, 0, 50, 50, 100), "child 2 position ok");
          assert.isTrue(positionEquals(c3, center, center+50, 0, 50), "child 3 position ok");
          assert.isTrue(positionEquals(c4, center, center+50, 50, 100), "child 4 position ok");
          assert.isTrue(positionEquals(c5, 250, 300, 0, 50), "child 5 position 