iOS code signing for a TestFlight release

WHAT THIS TESTS Whether you understand Apple's code-signing chain of trust and the concrete Flutter and Xcode steps to ship a build to TestFlight.

A GOOD ANSWER COVERS A signing certificate is an identity issued by Apple, paired with a private key held in your keychain; signing the binary with it proves the build came from your developer account. A provisioning profile is a document that bundles a specific App ID, the allowed certificates, the entitlements, and, for development, registered device UDIDs; iOS checks it before running the app. For TestFlight you use a distribution certificate and an App Store provisioning profile. The flow: register a unique bundle identifier and App ID, create the certificate and distribution profile in the developer portal or let Xcode automatic signing manage them, open ios/Runner.xcworkspace, select the team and signing in the Runner target, then archive the Release build and upload to App Store Connect, which feeds TestFlight.

COMMON WRONG ANSWERS Saying the provisioning profile signs the code; it authorizes, the certificate signs. Using a development profile for TestFlight. Forgetting that the bundle identifier must match the App ID. Ignoring that the private key must be present to sign.

LIKELY FOLLOW-UPS Difference between development and distribution profiles. What entitlements get embedded. How does automatic signing differ from manual. What is the role of App Store Connect.

ONE CONCRETE EXAMPLE To ship a beta, you set the bundle id to app.example, enable automatic signing in Xcode with your team selected so it provisions a distribution certificate and App Store profile, run flutter build ipa, open the resulting archive in Xcode Organizer, and upload it. App Store Connect processes the build and exposes it to TestFlight testers. The certificate established who you are; the profile authorized this exact app to be distributed.