Testflight while app is "waiting for review"

Question

We are in a hurry to publish an app for a customer, so yesterday we published an app to App Store and now is "Waiting for review".

Meanwhile, the customer aked if he could have a preview. My idea was to send him a TestFlight beta testing. I'm thinking in several options:

• Start an internal testflight for the build that is in review for team customer users
• Start an external testflight with the build is in review for other customer users not in the team
• Send a new build and start internal testflight for team customer users
• Send a new build and start external testflight for other customer users not in the team

What I'm not sure is on each case (internal/external testflight):

• Can I start a testflight testing for a build that is "in review"? And if I can, will it cancel the "in review" process for this build?
• Can I send another build while there is already one "in review"? And if I can, will it cancel the "in review" process for the previous build? If it will not, can I start a testflight for a new build while previous one is in review?

As said, the priority here is not to stop the "in review" process.

EDIT

I've been reading docs at https://developer.apple.com/library/content/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/BetaTestingTheApp.html and what makes me be scared is:

When you are done using TestFlight beta testing, you can submit the app for final review

So it seems that testflight is more like an step in the process than a parallel option in the process...

Answer 1

Would be nice to have had a reply after your "will give a try..."

So I had the same issues a few minutes ago:

• App is "waiting for review".
• And no internal/external testing available for the client.

Since the external testing will also need a review by Apple I went for the internal way. So I added my and the clients account to internal testing. Then I added the current build which is also in "waiting for review" state to the internal testing.

Result: It worked. I got the invite email and could download that build via TestFlight. The app is still "waiting for review".

Just in case someone else stumbles upon this question/answer here.