Is a runner card turned facedown still itself?
Facedown cards are no longer the same card they were before being turned facedown. In this example, Test Run's "if it is still installed" fails to trigger, and the cards stays where it is.

Based on Project ANCUR's answer to the question on twitter, which was favorited by Lukas (and therefore fairly authoritative, I suppose):


  No. By being turned face down, it is no longer the previous instance
  of Harbinger that Test Run has a reference to (it's not an instance of
  Harbinger at all, just an installed facedown runner card)