Postman Interview Questions 2026

Explain common HTTP status codes returned by APIs (2xx, 3xx, 4xx, 5xx). Differentiate between 401 vs 403, 404 vs 400, and 502 vs 503. How do you validate these in automated API tests?

Describe JSON Schema Validation and its importance in API testing. What is a JSON schema? How do you validate that an API response conforms to the expected schema using Rest Assured or Postman? Give an example schema for a user object with required fields and type constraints.

Differentiate between Path Parameters and Query Parameters in REST APIs. Give examples: /users/{id} vs /users?role=admin. When should each be used? How do you pass and validate them in automated API tests using Rest Assured or Postman?

How can nested JSON responses be handled in API testing? Show how to extract a deeply nested value (e.g., response.data.user.address.city) using Rest Assured's JsonPath, and how to validate arrays of objects within the response.

In Postman, how would you chain two requests so the second one uses an ID returned by the first, without hardcoding it?

How do you test a REST API that requires OAuth 2.0 authentication? Walk through obtaining a token (client credentials flow), storing it, using it in subsequent requests, and handling token expiry in your automation framework.

How would you test a payments API endpoint for race conditions where two simultaneous requests might both succeed at deducting from the same account balance?

How would you test that a "cancel ride" API endpoint correctly refunds a rider only when the cancellation happens within the free-cancellation window, and charges a fee otherwise?