You need cost-effective, reliable unit tests that assert Pub/Sub messages are processed by your subscriber in order. What approach should you use?

The Pub/Sub emulator provides a local, in-memory version of the Pub/Sub service, allowing you to test your application's Pub/Sub interactions without incurring costs or relying on the actual cloud service. This makes it ideal for cost-effective and reliable unit testing, as it ensures messages are processed in order within a controlled environment. Implementing a mocking framework would involve creating simulated Pub/Sub behavior, which can be complex to maintain and may not accurately reflect the real service's ordering guarantees. Creating a topic and subscription for each tester is expensive and resource-intensive, making it unsuitable for unit testing. Adding a filter by tester to the subscription doesn't address the need for a local, cost-effective testing environment and primarily serves to route messages, not to facilitate isolated unit tests.