Ludevic’s Test Subject is a double faced card that has the potential to transform when its activated ability resolves. This activated abitliy does two things, its puts a hatchling counter on Ludevic’s Test Subject and then if there are five or more of these counters on its at that point, the counters are removed and the card is transformed into Ludevic’s Abomination.

It is important to note that this transformation only occurs when this activated ability resolves and not at any other time. For example, if the Test Subject had five hatchling counters on it and it gains another when someone proliferates it will not transform.