API Testing Introduction: What and Why

API testing checks the behavior of application programming interfaces—request/response, status codes, and data—without relying on the UI. This post introduces what API testing is, why it matters, and how it fits into your QA roadmap.

What is API testing?

You send requests (e.g. HTTP) to an API and verify:

• Status code (e.g. 200, 404, 500).
• Response body (structure and values).
• Headers (e.g. content-type, auth).
• Performance (response time, if needed).

You test contracts, business logic, and error handling at the API layer. No UI required.

Why API testing matters

• Fast and stable: No browser or DOM; tests run quickly and are less flaky than UI-only tests.
• Early feedback: You can test as soon as the API is available, before the UI is ready.
• Coverage: Many flows are driven by APIs; testing them directly gives broad coverage with fewer tests than UI-only.
• Automation: APIs are easy to automate (e.g. Postman, REST Assured, pytest); they fit well in CI/CD.

Where it fits in your roadmap

API testing sits between unit tests (code-level) and UI tests (end-to-end). It is a core skill for Automation QA: you will design API test cases, use tools like Postman, and automate API tests in pipelines. The next posts cover REST, HTTP, Postman, and API automation.

Summary

• API testing = send requests, check status, body, and headers (and optionally performance).
• It is fast, stable, and easy to automate; it gives early feedback and broad coverage.
• It is a central part of the QA roadmap; master it before diving into UI automation.