public void AddElement_Valid()
{
PresentationDocument pres = PowerpointHelper.CreatePresentationWithOneEmptySlide("./testFile3.pptx");
ShapeTree shapeTree = PowerpointHelper.GetShapeTreeOfFirstSlide(pres);
List <int[]> list = new List <int[]>();
list.Add(new int[] { 1, 2 });
list.Add(new int[] { 3, 4 });
list.Add(new int[] { 5, 6 });
Shape polygon = PowerpointHelper.CreatePolygon(list);
PowerpointHelper.AddElement(shapeTree, polygon);
var errors = validator.Validate(pres);
Assert.IsTrue(errors.Count() == 0);
Assert.IsTrue(shapeTree.Count() > 0);
}