Why MockMotor has Postponed Execution
To mock callbacks or asynchronous replies, use Postponed Background Request
The Advanced section of the reaction page contains a Postponed Background Request configuration.
You can configure a request that will be executed after the current request is completed, with a specified delay, but with the same context - for example, the original request, the account (if any), and the generated response.
You can use it to simulate callbacks made by the mocked application, from basic webhooks to asynchronous transaction processing.