Counting everything even indirectly attached to the rig, you need exactly one length of rope for each system (sheet/traveller/vang/cunningham/outhaul), plus a clew tiedown (which can of course be a strap as well) and a mast retainer. Minimum blocks are all the sheet and traveller blocks, a vang cleat block and a vang key block. That's it. (And no difference between the rig sizes.)
In that case, you probably won't need to buy anything.
Just connect the end of the boom to the clew of the sail with a piece of line. Adjust the length for some (hand width) curve in the foot of the sail, but you don't need an adjustable outhaul for your test.
You also don't need an adjustable Cunningham set up. Just a piece of line around the vang tang will do.
You don't need a 'real' boom vang either, just a piece of line to connect the boom at (roughly the appropriate location) to the vang tang. In light weather even that may not be needed; I sure hope you will do your test in light weather!
You will need a traveler (can use cheap rope rather than fancy no-stretch rope. You will need the traveler blocks, but you really don't need the hiking strap for your test.
Do make sure you connect the tiller to the rudder head (there's a pin for that).
Also make sure you have a mast retainer (a line to keep the mast with the boat).
I think I covered all that is needed, but my Laser/ILCA brain may be a bit leaky...
More in general, there is a better way to test whether your hull is water tight. It involves soapy water and light pressure (through the drain in the stern).
Did you test whether the mast tube holds water?
Another common area that may leak is the bailer.
If your intention is just to briefly sail the boat you can just rig a couple of short lines with bowline loops on their ends to serve as blocks. Use a third line through the loops as many times as you like to achieve the purchase you want.
Per LaLi's question, it seems you can check for leaks more easily using a soap solution and VERY low air pressure applied to drain. Use a hand pump intended for inflating air mattresses, etc. More pressure and you may get a really big new leak!