Application Programming Interface
An application programming interface (API) defines the rules that allow different software components or systems to communicate with each other.
“A type of interface in which the components or systems involved exchange information in a defined formal structure.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Application Programming Interface?
An API specifies how one application can request services or exchange information with another application using predefined operations, protocols, or endpoints.
Communication: APIs enable software integration without exposing internal implementation details.
Standardization: Well-defined interfaces simplify development and maintenance.
Testing importance: Reliable APIs are essential for integrated systems and modern applications.
Real World Example
An insurance claims platform is connecting a claim intake service, a policy validation service, and a payment approval service.
Each part can look correct in isolation while the handoff between parts still fails. Application programming interface helps testers focus on the boundary where data, timing, and responsibility meet.
The tester checks payloads, error handling, retries, missing fields, and the order of service calls instead of only confirming that each screen appears.
The claims flow becomes more dependable because Application programming interface exposes defects that only appear when real components collaborate.
Practice Questions
Question 1
Which practice BEST protects API consumers during changes?
Question 2
Which test MOST directly validates an API contract?
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