Interoperability Testing
Interoperability testing verifies that a system can correctly exchange data and work together with other systems, platforms, or software it's meant to integrate with — different vendors' implementations of the same standard, third-party APIs, or legacy systems it needs to communicate with.
This shows up most clearly wherever standards leave room for interpretation: two systems can both claim to implement the same protocol or file format correctly and still fail to work together, because each made slightly different, individually reasonable assumptions about ambiguous parts of the spec.
Healthcare (HL7/FHIR), finance (ISO 20022), and any system built on open standards with multiple independent implementations are classic interoperability testing territory — testing isn't just "does our system work," it's "does our system work correctly with everyone else's."
