Testing many solenoids can be easy, but not so with the GM TEHCM units. Since the solenoids are contained within a single housing and connected to a TCM, testing is much more difficult. There are however test kits available that can make the process relatively simple. The test kits are produced by Kent-More and are model specific.
The DT-48616 is used for the GM 6T40 and the DT-47825 is used to test the 6L80 and 6T70 models. The test harness in the kit is only for the 6L80. The test harness for the 6T70 is part number DT-47825-20 and is available separately. Utilizing a GM Tech 2 scanner each individual solenoid can be air tested for proper operation.