public void AssertThat_LineSegment_FindsIntersectionAtOne()
{
var a = new LineSegment2(new Vector2(10, 0), new Vector2(0, 0));
var b = new LineSegment2(new Vector2(-10, -10), new Vector2(20, 20));
var i = a.Intersects(b);
Assert.IsTrue(i.HasValue);
Assert.AreEqual(1, i.Value.DistanceAlongA);
}