Test the binary you actually ship
A green test suite proves that the source behaves in the test environment. It does not prove that the packaged program works on a clean machine.
Packaging changes the system. Files move. Runtime dependencies disappear. The working directory changes. The user has a different shell, a restricted PATH, and none of the shortcuts from a developer checkout.
Build the release artifact early. Install it the way a user will. Start a fresh project through the public command, run the real workflow, and inspect what the distribution plan actually includes. That is where missing assets, accidental source dependencies, and environment assumptions become visible.
Source-level tests protect the implementation. Artifact-level tests protect the product.