Api Testing
API testing verifies that an application programming interface functions correctly, reliably, securely, and efficiently without relying on the user interface.
“A test approach performed by submitting requests to a test object using its application programming interface.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Api Testing?
API testing focuses on requests and responses exchanged between software components. It validates business logic, error handling, performance, and security at the service layer.
Interface validation: Confirms APIs return the correct data and status codes.
Advantages: Faster and more stable than many user interface tests.
Coverage: API tests verify functional and non-functional requirements.
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. Api testing 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 Api testing exposes defects that only appear when real components collaborate.
Practice Questions
Question 1
Which check BEST belongs in API testing for an order service?
Question 2
Which failure MOST likely indicates an API contract issue?
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