A testing tool that simulates a PSP updating the status of a refund asynchronously.
This mock PSP server supports several test senarios for refunds, based on the
"amount" field in the request payload from Uber:
Amount == 4.00 - the mock PSP fails with 400 (Bad request).
Amount == 5.00 - the mock PSP fails with 500 (Internal server error).
Amount < 1.00 - the mock PSP returns FAILED status to Uber immediately.
Amount >= 1.00 and < 5 - the mock PSP returns SUCCEEDED status to Uber immediately.
Amount == 6.66 - the mock PSP returns PENDING status to Uber immediately, followed by a FAILED callback 2 seconds later.
Amount == 7.77 - the mock PSP returns PENDING status to Uber immediately, followed by a SUCCEEDED callback 2 seconds later.
Amount == 8.88 - the mock PSP returns PENDING status to Uber immediately, followed by a SUCCEEDED callback, followed by a FAILED callback.
other values - the mock PSP returns PENDING status to Uber immediately, without any callback.