The Boring Bits; Wiring it up:
On their sides they go so copper bus wires can be installed underneath. The test track gets a pair and the switching/shunting tracks get a pair all their own.
Drop connections from each side of each set of points are soldered to the rails on one end and to each respective bus on the other.
The rail joints are also soldered, making for an extremely robust current path to all trackage with no mechanical connections to fail over time.
The result has two circuits, one for the test track and one to the shunting tracks. A double-pole double-throw electric switch will select between them: both cannot be powered at the same time, so testing a loco on the test section doesn't mean you need to remove what might be on the shunting tracks.
Because this comes apart into two four-foot sections, a keyed plug is included so, when one mechanically connects the two sections together, one electrically connects them together thus:
Today, the last wiring task, the power tap through the afore-mentioned DPDT switch will be installed and connected. Then we can actually test this thing with a loco. Given that goes to plan, its on to the finishing and scenic'ing.