I don't want to sound pessimistic, but I wouldn't get too excited just yet. At 7 days you should be able to veins and a small dark spot......if it's developing. IMO 3 days is too early to tell much of anything.
Good luck with test egg, one other stupid question is do you have a hatcher? If not you dont want to add the silkie eggs or you will have a problem when the test egg gets to day 18. Not good for either test egg or the silkies. Jenn
On day 18 for the test egg you will need to stop turning and up the humidity, and it wont be time to do that with the silkie eggs which could cause them not to do well. You will need to move the test egg to a hatcher with the humidity raised so that it can hatch while the silkie eggs finish getting to day 18.