public void TestOpAdd()
{
float x1 = 2, y1 = 5;
float x2 = 10, y2 = 15;
float x = x1 + x2;
float y = y1 + y2;
Vector2D v1 = new Vector2D(x1, y1);
Vector2D v2 = new Vector2D(x2, y2);
Vector2D v = v1 + v2;
TestHelper.AssertEquals(x, y, v, "Testing v1 + v2");
}