Togai, an API-first metering and billing solution service, utilizes a microservice architecture, making it essential to have both local integration tests and unit tests to ensure smooth operation. When multiple processes are involved in accomplishing a task, there are many moving parts that need to be coordinated to ensure smooth operation, requiring careful consideration of various factors such as communication methods, testing strategies, and resource management. Togai uses JUnit5 for testing Kotlin services, running Postgres, Timescale, and Redis inside the test container while tests run on these containers, including both local integration tests and unit tests. The platform also optimizes consumer flow tests by using message queues to reduce service load and individualize each service, reducing the probability of system crashing and improving resource utilization. To ensure deterministic testing, Togai addresses questions such as asserting failure in between processing messages and determining when the consumer has completed its job, setting timeout limits and stress testing channels for performance benchmarking.