How are Teams apps tested?

I had submitted a Teams App for approval. The approval has Failed with primary reason being "We could not install your app"

I would like to know how exactly the app is tested. I had submitted a zip file containing the manifest.json as part of the submission. How is the validation team going about using the zip file and manifest.json? I am able to install the app(bot) without any issues with my test accounts for 1:1 chats. If the validation team can let us know the steps they are following to test the app, then we can try replicating those to see if we get the same error.

The testing procedure in the Microsoft documentation is as mentioned in this link: http://ift.tt/2vEfDF4

Is the validation team is trying to sideload the app into a team as a result of which they are seeing an error on installation. The app is not meant for use in teams. It is for use in 1:1 chats only. Listing the steps that the validation team is following will be of much help!