public void AddOverlay_WhenOverlayIsNotNullAndIsNotPresent_DoesNothing()
{
var overlayManager = new OverlayManager();
var overlay = new StubOverlay();
overlayManager.RemoveOverlay(overlay);
Assert.Count(0, overlayManager.Overlays);
}
public void RemoveOverlay_WhenOverlayIsNull_Throws()
{
var overlayManager = new OverlayManager();
Assert.Throws<ArgumentNullException>(() => overlayManager.RemoveOverlay(null));
}