Offline, read-only simulation of declared schema migration steps over an exported fixture. This is a deliberate safety adaptation of a database rehearsal: it does not create a database, connect to one, execute SQL, inspect production, modify fixture files, or delete data. It checks only the narrow declarative schema operations listed below; it cannot prove real SQL behavior, data transformations, locking, or database rollback safety.
This walkthrough uses the tool's public README and checked-in example files. Run the command from a repository checkout with Node.js 22+.
Run the checked-in example
node bin/migration-rehearsal-runner.mjs --root examples/pass --input snapshot.json
node bin/migration-rehearsal-runner.mjs --root examples/fail --input snapshot.json
npm run checkRead the result
--help prints usage. Normal runs emit one JSON report on stdout: exit 0=pass, 1=fail, 2=incomplete or invalid configuration. Invalid options or root produce empty stdout. An unreadable, undecodable, malformed, or out-of-root named input produces an incomplete report. The input is realpath-confined under the root; UTF-8 decoding is strict and duplicate decoded JSON keys are rejected. No files are written.