Interoperability
Interoperability is the degree to which two or more systems can exchange information and use the exchanged information effectively.
“The degree to which two or more components or systems can exchange information and use the information that has been exchanged.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Interoperability?
Interoperability focuses on successful communication and cooperation between independent software systems through standardized interfaces or protocols.
Information exchange: Systems transfer data correctly.
Meaningful use: Exchanged information must be interpreted consistently.
Testing focus: Verify communication across heterogeneous systems.
Real World Example
A travel booking platform needs its checkout service to exchange passenger and fare data with three different airline reservation systems, each built by a different vendor.
Each system passes its own functional tests in isolation, but nobody has confirmed that data leaving one system is interpreted correctly by the next. A date, currency code, or fare amount can cross the boundary without an error being thrown and still come out wrong on the other side.
The tester designs cases that specifically exercise the handoff between systems: a booking created through one airline's API is checked against how the internal reservation system displays it, confirming that time zones, decimal separators, and currency codes all survive the exchange with the same meaning.
A defect surfaces where fares from one partner were being silently rounded during the exchange — something neither system's own test suite would ever catch, because each one worked perfectly on its own. Testing Interoperability means testing the seam, not the endpoints.
Practice Questions
Question 1
A payment gateway correctly processes every transaction on its own, but when it forwards order totals to a partner airline's reservation system, decimal points are occasionally dropped so fares display as whole numbers. Both systems pass their own functional tests. Which concept is MOST directly being tested when a tester checks this data exchange?
Question 2
A hospital system must exchange patient records with an external lab's system. Which test case BEST targets interoperability?
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