Where in the Mobile Hub after generating does the code reference the user pool? I have searched the project for my user pool name: testing_userpool_MOBILEHUB_xxxx but can't find it anywhere. Is it stored in a constants somewhere? I am new to Mobile Hub.
You don't mention the language, but...
In iOS, there is an Info.plist file. Look under AWS/CognitoUserPool/Default for the four keys that identify the user pool.
In Android, there is a file in app/src/main/java/com/amazonaws/mobile called AWSConfiguration.java that contains the definitions.
In JavaScript, you will adjust the AWS.config global variable. This is generally set up in a file called aws-config.js within your project.