When working with external services, you often want to run tests without depending on the external system's relability or performance. As you write tests for features that depend upon the @daffodil/external-router/driver you will find yourself looking for a simple way to meet the DaffExternalRouterDriverInterface interface requirements without over-complicating your tests. In these scenarios, having a testing driver that emulates the behavior of an external service is extremely useful. The DaffExternalRouterTestingDriver is well-suited for these purposes.
The DaffExternalRouterTestingDriver of the @daffodil/external-router/driver/testing is useful for Unit Tests, Integration Tests, and simple Acceptance Tests where you don't want to depend on an external service over HTTP.
See the testing guide for example usage.