I would suggest that any circuit you make is designed with global standards in mind. For CE there are specific tests to be performed, figure of 8 circuit to be run.
Bear in mind arrangements for fuel consumption tests in accordance with global standards.
If you are taking from a manufacturers perspective then build something which not only allows for the endurance testing, but also component, gradient (tilt ramp), fops and rops etc. as well as general testing of every forklift that rolls off the production line as a final seal of approval.

One of the best parts of a test facility is traceability in my opinion. In case of field complaints it is great to be able to pull up digital data showing that a vehicle was correct when it left the factory.

The previous manufacturer I worked for we had two test areas one for the testing of design (tilt table test, rops/fops, fuel consumption, noise, EMC/EMF compliance) and then a separate area for final testing of production forklifts including the figure of 8 circuit, automated load test with tie down for the forklift, dyno (speed) test and service and park brake testing all of which was logged digitally against the chassis via RFID and barcode.
For cabin testing we installed a booth for spraying water all over the truck to test for leaks.

Better to review what your goals are for the test area and what you wish to achieve from your testing, before even thinking about layout etc.