Pipe tests are usally in the 6 G position where the pipe coupon is "fixed" at a 45 degree angle.  The procedure you are talking about is using 5P+ for the root and 7018 for the fill and cap. Is this what you mean? My experience is that (unless it is a guided bend test) you'll be welding 2" XX heavy (I think schedule 120) pipe which is nearly 5/8" thick. They usually will x-ray the weld and determine the quality per ASME B.31.1 or B.31.3. This would be a standard new hire test for most shops or construction companies which specialize in industrial piping.
Anyway, hopefully you are not running a 7018 open root cause that is a horse of a different colour and it is not easy. However, IF you are using 5P for the root and you have run some then all you'll have to do is focus on getting the 7018 down pat. Say you'll be welding the 2 " I mentioned above. Use 1/8" 5P+ for the root and then use 3/32" 7018 for the balance. Use 85-95 amps for the 7018 as I assume you can already put in a decent root with the 5P so we don't need to talk about that. Start at 6 o'clock (bottom of pipe) and maybe 1/8"-1/4" to the other side , away from direction of travel. Keep the rod angle slightly above perpendicular to the joint and a 5-10 degree travel (drag) angle. Once you light up, you'll run about an ich of metal and then you'll be "pushing" the molten pool uphill. That's where you want to be. Reall, to me the 1st pass after the root is critical because after you grind out the root (again, i assume you know this part) you have thinned out the deposited metal of the root and you do not want to burn it out and open up a hole which will happen when practicing. Keep the arc tight and move delibertly enough so the puddle is slightly bigger than the rod with the flux on it. When you clean off the 1st pass of the slag. it should be not much bigger than 3/16" wide to 1/4". Grid your stops & starts. So you have 1/4 of a pass done, go to the other side and go from 6 o'clock to the other direction. You should notice one direction is more awkward then the other. Until you have done a few coupons this will always be the case, so don't get discouraged, just figure out what it will take to get comfortable and make the "hard" side look as good as the "easy" side.
So, once you have the 1st pass completed, you are on easy street as the rest will be a series of stringer beads to fill it up. No more chance of burning thriu the root. Keep the same rod angle and travel angle with the fill passes and you'lll be able to jack the heat up atleast 5 more amps on these passes(perferrabley 10 amps). Fill to 1/16" from flush.
To pust a decent cap down, you need to concentrate and really pay attention to how you lay down the beads. Remeber i said 1/16" from flush? This is so you can still see part of the bevel which you will be covering with the cap. When you put on the cap the 1st bead (of a 3 bead cap) needs to just barely cover the bottom edge of the exposed bevel. So you'll need to make the molten pool just barely cover the exposed bevel and try and keep a good line around the pipe. If your 1st bead is nice and straight, then the other 2 beads have a good chance of being the same way. Drift down too far past the bevel.....you'll have a big woop-dee-doo that will look like crap. Avoid this at all cost. We assume you put down your 2 beads and you are on the last one. Turn the heat up 5-10 more amps and really "Move" as all you are doing is covering the top part of the bevel and it should not take much metal to do this. Keep the rod agle above the perpendicular 5-10 degrees because if you don't.......you will have a droopy 3rd bead probably with undercut. Some contractors just want to see if you can weld and they amy not actually send the coupon out for x-ray but don't count on that.
KEY POINTS:
Keep the joint clean. Grind when necessary.

IF your root burns out: 1 you are too hot
                                2 you are moving too slow
                                3 you did not have enough root re-enforcement

LOOK hard  for porosity and remove it completely before notching another rod as it is an auto matic bust-out for x-ray.

Get comfortable: I always do the hard side first as it forces me to make it good and I know the easy side is that......easy.

Shorten the rod: you can either bend the rod after notching it or knock the flux off before hand and clamp it there. You'll be alot more steady.