public void RotatePolygon(string points, double angle, string expectedPolygon)
{
var testElement = new Polygon2D(from x in points.Split(';') select Point2D.Parse(x));
var expected = new Polygon2D(from x in expectedPolygon.Split(';') select Point2D.Parse(x));
Angle a = Angle.FromRadians(angle);
var result = testElement.Rotate(a);
Assert.IsTrue(expected.Equals(result, 0.001));
}