ERJ-170 Captain reported procedures were not followed by Contract Maintenance during a ground pressurization check to ensure proper operation of the cabin pressure control system. The pressurization check was done with the flight attendants on board and did not follow the AMM procedures.

Narrative

I will start this report by stating I am not a licensed Mechanic in any way. I am a Captain that had an issue with Contract Maintenance having to do a pressurization test at the gate once I arrived at the gate. The previous Captain who brought the plane in wrote in the log; intermittent whistle on the L1 Door; which is the reason for the test. I have never been on an airplane during a pressurization test. During the test; we had the doors closed with me; Contract Maintenance in the flight deck - only one Maintenance guy was present - and the flight attendants sitting in the cabin. The First Officer was on the jet bridge. Company Maintenance emailed the appropriate procedure to my iPad; because the Contractor did not have access to email; which I pulled up the procedure and gave it to Maintenance. Part of the procedure was to clear the ramp area which I had the First Officer do and have all the doors closed and locked. Then; I was asked by the Contractor to put the pressurization mode into manual and adjust the cabin altitude to the down position and close the outflow valve. They did not seem to know where the knobs were so I showed him and put the knobs where they should be and adjusted it; holding the knob in the down position. I did not close the valve all the way because the pressure change was rapid and got really uncomfortable and the psi was climbing quickly as well. Cabin altitude rate was 3;000 - 4;000 FPM and differential pressure was 4.3 at maximum. I really had no direction nor did Maintenance seem to care if the procedure was done properly. I opened the outflow valve; opened the doors; and they signed off the logbook with no apparent leak in the pressurization and we went on our way to ZZZ. After leaving I reviewed the procedure and realized that Contract Maintenance did not go through the procedure step-by-step and deviated from proper procedure. They ignored many safety warnings; including everyone having medical clearance to be on board during the test and not have underlying health issues; and if the procedure isn't followed correctly it could cause injury or damage to the aircraft. The flight attendants should not have been on board. Thankfully there was no one that was injured and the aircraft did not seem to be damaged.The procedure was more involved than just closing the outflow valve. The packs and bleeds were supposed to be off during the initial test; which is where the deviation began. With the bleeds and packs off the outflow valve should be closed then opened again. The next step is to then turn the APU bleed on and use either Pack 1 or Pack 2 to pressurize the cabin and follow AMM (Aircraft Maintenance Manual) task to supply pneumatic power through the APU.I am not a Mechanic and do not know the procedure and I do not know what was communicated between the Contractor and Company Maintenance. I put the safety of myself and my flight attendants in the hands of Contract Maintenance; which I regret and wish I handled it better. Next time I will surely include Company Maintenance and have them walk through the procedure step-by-step and see that it is performed properly and safety is not compromised. Follow proper procedure; follow checklist.