ISX Injector Leak test

[JB Farm]

Hello all, first time poster. I have a CM870 setting on the floor. Engine is out of a wrecked truck. The owner said he was told this engine had a bad injector but it did not get repaired before being in wreck. My question is with injector leak test. Can I perform that test with engine on the floor? I know I can do the test but will it be accurate? I've always used the starter to see if there's leakage and then barred engine by hand if I had bubbles. Does the engine need to spin faster to initially check for bubbles?