Free worked exercise · Original synthetic data

Mask related JSON fixtures without losing example ID relationships

A users file and an orders file share an ID. Transform both in the same batch to preserve that relationship with explicit rules.

Run the synthetic proof

Not run yet. Supplied synthetic fixtures only.

No account or payment needed. This exercise sends no input-upload requests and stores no inputs. Normal host access logs may exist.

Select related paths

The free recipe uses /users/*/id and /orders/*/userId with the same USER namespace. Selected email fields receive an example address. Inputs, rules and expected JSON are included.

Use one batch

The same typed source ID receives the same token within the shared scope. Numeric 7 and string "7" remain distinct. Null stays null. These tokens are not permanent identity keys.

Separate runs reset the token map

Two unrelated IDs can each become USER_001 in separate calls. Combining those independently transformed files could create a false relationship. Keep related documents in one batch or design a reviewed mapping workflow.

Inspect what remains

Unselected order details stay intact. The manifest lists changed paths instead of source values. Review remaining values and field names before sharing. Equality preservation does not prove anonymity or automatically detect personal information.

Check the supplied expected files

The local runner compares both generated documents with the original expected fixtures. It exercises one synthetic case. The engine, first recipe and license are preserved from the already-public free sample; no other paid recipe is included.

Presidio offers PII detection/redaction for a different task. Fixture tokens do not provide equivalent privacy protection.

Download and reproduce

Download the free exercise ZIP

Extract the ZIP and run with Node.js 22+:

node run.mjs
node exercise.test.mjs

No npm install or API key. Read the README and license before adapting.