public void TestHashCode()
{
var rect1 = new Rect2d(1, 2, 3, 4);
var rect2 = new Rect2d(1, 2, 3, 4);
Assert.Equal(rect1.GetHashCode(), rect2.GetHashCode());
rect2.Shift(1, 1);
Assert.NotEqual(rect1.GetHashCode(), rect2.GetHashCode());
}