You not only should, but have to upload a release build:
Using TestFlight to beta test iOS apps involves submitting an app to iTunes Connect that is signed with your App Store distribution provisioning profile. […] This is the preferred method of beta testing because it does not require you to re-build or re-sign the submission for App Store publication.
Source: Technical Note TN2407: iOS Code Signing Troubleshooting Index
If you want to test a development build, you should look into HockeyApp or similar beta distribution methods.