How often have you heard "it's gonna be hard or impossible to cover this part of our backend application"? I've heard a lot. Because our modern application always involve databases, message queues, 3rd party services. What if I tell you, that I can cover even logs with tests, values of custom application metrics, apps that involve Google Cloud Storage, Google Data Storage, Kafka, Redis, Lambdas, DynamoDB, Aerospike, S3. I work in highload project without manual QA's at all. And I'm confident in my everyday releases, so should be you.