Upgrade test (adb install -r

When I am ready to release a new version to Google Play store, I usually test upgrade process by downloading an old APK and simulate upgrade with a new APK - adb install -r <app.apk>.

I tried to do the same for app published on the amazon app store, but I cannot do it. When I try to install the new APK via -r switch, the ADB complains about different certificate. Since we do not sign APK during upload procedure to the Amazon App Store, I guess they do some kind of signing before releasing the app.

How can I test upgrade process for the Amazon APK?

I do not have commit that created the APK that had been uploaded to the Amazon APK. I only have the code I fixed.

I tried by downloading app via amazon app store onto my device and then backup it to APK. But during this process I got the error I mentioned on the top of this question.

Amazon developer console does not allow us to download APK as well.