Hi @JoshuaAAC,
Thanks for sharing this question with the community. Congrats on getting your flow setup with an automatically generated code! Very wise decision to incentivize customers and make it easy for them to complete their purchase.
Now on to the solution. The best way to test a flow and receive a live coupon code is to first clone the flow. Next, strip out any time-delays and non-coupon-containing emails in the flow so you’re left with just the trigger and the flow email containing the coupon.
Next, turn the email in the flow to Manual status and then enter yourself into the flow by taking the triggering action for the flow, (in your case by starting a checkout) that will queue you up to receive the email.
Flow email in Manual ModeWhen a message's status is manual, at send time, each recipient will move to the Needs Review tab. Click on the flow email and then on “Needs Review” on the left-hand side bar.
Emails in “Needs Review” statusFrom here, you’ll want to click on the “send” button next to your email address only (don’t click send all). And if all goes as expected, you will receive the live coupon code in your inbox.

I hope that’s helpful!