It then writes a report. By default stdout carries the human-readable summary; --json replaces it with the machine-readable report, which is the form to pipe into a JSON parser. Either way stderr carries a one-line summary and any operational diagnostics, and never report data.
This walkthrough uses the tool's public README and checked-in example files. Run the command from a repository checkout with Node.js 22+; inspect the source before using it on your own files.
Run the checked-in example
# a recording that replays cleanly: exit 0
node bin/function-call-replay-harness.mjs \
--recording examples/recording.json \
--registry examples/registry.json
# the same registry against a recording that diverges: exit 1
node bin/function-call-replay-harness.mjs \
--recording examples/recording-divergent.json \
--registry examples/registry.json
# the machine-readable report
node bin/function-call-replay-harness.mjs \
--recording examples/recording.json \
--registry examples/registry.json --json
npm run check # lint, tests, the runnable example, and npm pack --dry-runRead the result
npm run example runs the passing case and npm run example:failing runs the divergent one.
Where this check stops
Every limit is enforced, reachable from its own flag, and covered by a test that drives it through the command line.
Before adapting the command to your own workflow, review the accepted inputs, exit codes and safety boundaries in the README.
Compiled with AI assistance from checked-in public documentation and example scripts. Run the example and review the repository's current documentation before relying on its result.