You can't spin up a maternity ward in CI. But you can get 274 tests and 90% coverage without one.
Some Background
I've been building an open-source Maternity HL7-to-FHIR Pipeline that converts legacy HL7 v2.5 messages into FHIR R4 resources with Australian and European FHIR profiles. The pipeline has three layers: Mirth Connect for HL7 ingestion, FastAPI for FHIR transformation, and HAPI FHIR Server for persistence.
If you want the full architecture story, the first article covers the end-to-end design, and the second article explains why I split responsibilities between Mirth and FastAPI.
This article is about the part that made me confident enough to publish the whole thing: the tests. Specifically, how to build a reliable test suite for a healthcare integration pipeline when you don't have access to a hospital system, a live HAPI FHIR server, or an MLLP connection.
