Give it an explicit interface matching the installed version. Unsupported calls must fail. Then use identified response examples to test parsing and the expected screen state separately.
Keep those captures, but label the version gap. They can help investigate the parser without becoming the authority for the intended interface. Compare against the actual installed API contract before calling the substitute faithful.
When I've handed over test results, people read passed and stop there; who will see exactly which response cases you exercised and which are still missing?
Also distinguish a valid negative fixture state from a failed request. Both may contain something false, but one is an observation and the other leaves you without a current observation.
Fixed in the offline version. Valid absent and failed read display differently. Thanks Rachel. Malformed responses and stale-value presentation still need tests.
Leave those gaps on the handover list. The corrected example is useful evidence about the application; comparison with the real controller remains another step.