Integration testing:
test that neighbour ports are set up, from state variables, on first pass of rules
test the input queue works
testing if a car leaving the mini roundabout correctly composes it's information and sends out the data to the port.


we can see in the log that starting at 100 ms, the neighbour ports are set to the state variables:
...
0 / L / Y / 00:00:00:100:0 / roundabout(1,1)(12) / out_directionport /      4.00000 / roundabout(02)
0 / L / Y / 00:00:00:100:0 / roundabout(1,1)(12) / out_isexitport /      7.00000 / roundabout(02)
0 / L / Y / 00:00:00:100:0 / roundabout(1,1)(12) / out_numhopsleftport /      0.00000 / roundabout(02)
...


log file shows the car entering the roundabout from the queue:
0 / L / Y / 00:00:00:100:0 / roundabout(4,4)(39) / out_exitnumberport /      7.00000 / roundabout(02)
0 / L / Y / 00:00:00:100:0 / roundabout(4,4)(39) / out_numhopsleftport /      5.00000 / roundabout(02)
0 / L / Y / 00:00:00:100:0 / roundabout(4,4)(39) / out_speedport /      2.00000 / roundabout(02)
car moves around roundabout to exit # 7 (see roundabout.log2)
then car's data is composed and outputted with numhopsleftport decremented by 1:
0 / L / Y / 00:00:00:900:0 / roundabout(1,1)(12) / out_west /    742.00000 / roundabout(02)