You can peek inside the fork hole and kind of see it all working. Testing for hold is actually fun and easy. Just go to an open parking lot, where there's nothing to hit, and from a slow roll with your foot completely off the clutch pedal, give it a quick half-throttle and your tires should break away smoothly and quickly almost as if you're on packed snow. Take a look at your marks and you should see two nice, even marks, assuming you have an LSD. Now, if you try that and smoke starts coming out of your tunnel, and your revs go up and your tires hold, then the clutch ain't holding.
As to how far the clutch slave and fork should move, here's a video of mine: