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Data Transformation intermediate 12 min

Verify an Implemented JSON Contract

Compare implementation evidence with declared intent so a passing example does not hide an unfinished contract change.

Scenario

The service change is merged, but the implementation may have skipped a declared field, changed a value kind, or removed a deprecated field early. A green example test is not enough to prove the declared plan was carried through.

Broken input

{ "user": { "id": "usr_182", "name": "Ada", "locale": null } }

Goal

Compare an implemented local payload with the Current-to-Proposed declarations, keeping contract mismatches separate from ordinary example differences.

Tool sequence

  1. Open Toolzy JSON Plan and restore the local plan bundle.
  2. Set Implemented from Source or paste a privacy-safe implementation response.
  3. Run implementation verification and review declared mismatches first.
  4. Read ordinary example differences separately; they are not automatically contract failures.
  5. Export a redacted review artifact only after checking the exact paths that were removed or replaced.

Checkpoint output

Declared mismatch: $.user.locale is null but declaration requires a non-null default
Example difference: $.user.name has a different display value

The defaulted field is a contract concern. The display value may be ordinary fixture variation.

Common mistakes

  • Comparing only the implementation and Proposed examples without loading declarations.
  • Treating every example value difference as a contract failure.
  • Exporting a redacted artifact without reviewing unmatched redaction rules.
  • Reusing a local bundle as a cloud share link.

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