The build passes. The pipeline moves. Hours of code are ready to ship—until one hidden connection fails. Integration testing sub-processors catch what unit tests never see. They reveal how every piece of your system talks to the services beneath it, including the subcontracted processors your architecture relies on.
Sub-processors are third-party services or components working inside your stack. They can run background jobs, handle data transformation, store assets, or push notifications. Your core platform hands them tasks. If they break, you break. Integration testing ensures those handoffs work exactly as expected.
Testing sub-processors starts by identifying every dependency inside production paths. Map them. List the APIs, queues, and jobs fired downstream. For each, define test flows that touch real endpoints or realistic mocks. Run the same tests during CI to catch failures early, before staging or production.
Pay close attention to contracts. Sub-processor updates often change payloads, authentication rules, or retry logic. Integration testing should include contract validation—checking that request formats and responses match spec—and error path coverage, so your main process survives when a sub-processor throws exceptions or times out.