I think gross modifies test here. I am not an expert but "gross test" does seem to be a technical terms for these type of failsafe tests.

Here are some examples:

FOR LEAKS:
Spray Probe: Provides Maximum Sensitivity
For this technique, the leak detector is hooked directly to the system under test and the inside of the system is evacuated. Once an acceptable vacuum is achieved, helium is sprayed discreetly on the outside of the system, with particular attention being paid to any suspect locations. Any leaks in the system, including defective welds (caused by cracks, pin holes, incomplete welds, porosity, etc.), flawed or missing gaskets, leaks due to loose clamps, or any other defect will allow helium to pass and be readily detected by the machine. The source of any leaks can then be accurately pinpointed and repaired.

The spray probe process is used to achieve the highest level of sensitivity. The equipment being used dictates the maximum sensitivity achievable; in Jurva Leak Testing’s case it is 2x10-10 std cc/sec. This technique does require that the system being tested is relatively leak tight prior to testing, as an ample vacuum is required for testing. However, by using special throttling devices a gross test can typically be performed. The gross test should eliminate any major leaks, permitting the use of increased sensitivity.
http://www.jurvaleaktesting.com/HeliumLeakTesting.html

It might be worthwhile to pickup a $30 leakdown tester and see what’s going on with that engine. You can do a gross test just with an air supply into the plug and listening.
http://www.abbysguide.com/ope/discussions/49200-54-1.html

TESTING A MOTOR
Off-line:
* Insulation resistance test / polarization index - gross check for insulation condition and dryness. (IEEE43)
* Winding resistance check - gross test for loose connections or shorted turns (normally shorted turns would
* DC Step voltage test - potentially destructive test which is more sensitive to insulation anomalies than simple insulation resistance / P.I. (IEEE 95.)
http://maintenanceforums.com/eve/forums/a/tpc/f/7161085912/m...

other:
A gross test was conducted
to test the water-repellent coating on the outer
layers of the lens surfaces. All the lenses were
wiped with a cloth, firstly with water and then
methylated spirits and the patterns of the droplets
that they formed on the lenses were observed.
http://saoa.co.za/publications/saoptom/2003/sept/high/Journa...