What is API Testing?
Turkish: API Testi
API testing validates endpoint responses, error codes, performance, and authorization behavior through repeatable test scenarios.
What is API Testing?
API testing checks software directly at the endpoint level instead of through the user interface. The goal is not only to see whether an endpoint returns “200 OK”, but to prove that request payloads, authorization rules, error cases, and performance limits behave as expected.
How Does It Work?
An API test starts with a defined request: HTTP method, URL, headers, token, and body. The test then checks the response code, JSON schema, required fields, business-rule output, and error messages. Negative scenarios matter as much as happy paths; missing tokens, invalid data types, unauthorized users, and boundary values should all be tested.
Tests can be organized as manual collections, automated integration tests, or contract tests that run in a CI pipeline.
Business Use
In payment, shipping, accounting, and CRM integrations, an API defect can stop orders or invoices from moving. API testing reduces release risk and catches external-system changes early. Postman is useful for exploration and collection management; a unit test verifies isolated internal logic, so it complements API testing rather than replacing it.
A strong test suite covers the successful flow, expected failures, authorization, rate limits, and backward compatibility together.
Related Terms
API contract testing compares consumer expectations with provider responses through contracts such as OpenAPI or Pact.
PostmanPostman is an API collaboration platform for sending requests, organizing collections, writing tests, and sharing documentation.
Unit TestA unit test verifies a small code unit such as a function or class quickly and automatically while isolating external dependencies.