@GarrettPhillips is right. The only extra steps company portal does is download the intunewin package and extract it.

I use a VM for testing installs. I copy the files and the script over to the VM, and run the powershell script. If everything installs as it should, I package it, and upload it.

If you use a custom script to detect if it installed correctly, you can also run that on the VM to validate it works as expected.

When we test from company portal, we assign the app to a specific group that only contains test accounts we use so we can verify from an end user point of view.