void TestAddition (Vector2 a, Vector2 b, Vector2 expected )
{
// This test asserts the following:
// a + b == expected
// b + a == expected
var result_1a = a + b;
var result_2a = b + a;
Vector2 result_1b; Vector2.Add(ref a, ref b, out result_1b);
Vector2 result_2b; Vector2.Add(ref b, ref a, out result_2b);
Assert.That(result_1a, Is.EqualTo(expected));
Assert.That(result_2a, Is.EqualTo(expected));
Assert.That(result_1b, Is.EqualTo(expected));
Assert.That(result_2b, Is.EqualTo(expected));
}