Were there scenarios where an event came from an external system rather than from your microservice?

Yes, such scenarios are common, especially in architectures with microservices and integrations with external systems.

For example, in testing microservices, it is often necessary to verify the processing of events coming from external sources — these can be messages from queues (Kafka, RabbitMQ), webhooks from third-party services, events from API providers.

In such cases, it is important to:

• Model or use real external events to test the microservice's response.
• Verify the correctness of processing, validation, and subsequent actions based on these events.
• Ensure that the microservice integrates correctly and does not lose events.

For example, during testing a payment service, an event about a successful payment may come from an external payment system, and it is necessary to verify that the microservice correctly updates the order status.