API Security and Testing Questions

Comprehensive coverage of testing and securing application programming interfaces. Includes designing, implementing, and automating tests across functional, integration, regression, and security areas. Core topics include authentication and authorization models and how to validate them in tests; request and response validation and schema enforcement; data format testing for JavaScript Object Notation and Extensible Markup Language; contract testing and integration validation; rate limiting and denial of service protections; input validation and injection attack detection; sensitive data exposure detection and prevention; business logic flaw analysis; fuzz testing; and penetration testing integration. Also covers test automation strategies and tooling such as Postman, Newman, and REST-assured; mocking and stubbing downstream services; testing complex behaviors across microservice architectures; test environment and test data management; and integrating automated API tests into continuous integration and continuous delivery pipelines. Emphasizes automated security testing workflows including reconnaissance, authentication and authorization checks, injection attack simulation, data exfiltration checks, and incorporation of API security into penetration testing and remediation processes. Finally, addresses monitoring, observability, runtime protections such as API gateways and web application firewalls, and best practices for secure API design, testing, and ongoing validation.

HardTechnical

57 practiced

Design an automated scanning job to detect secrets or credentials leaked in API responses, test artifacts, and logs that run as part of CI. Include the detection heuristics (regex, entropy, contextual rules), how to store whitelists, triage pipeline for results, and mechanisms to prevent storing discovered secrets in the CI system or exposing them to developers.

EasyTechnical

48 practiced

Using REST-assured in Java, write or describe a concise automated test that verifies a protected endpoint returns 401 when no authorization header is provided and returns 403 when an authenticated user lacks required scope. Include the key assertions and test setup you would use.

MediumTechnical

48 practiced

Write or describe an automated integration test that uses WireMock to simulate a flaky downstream service which sometimes returns 500 and sometimes delays responses beyond timeout. The test should verify that the API under test correctly falls back to a cached response or returns an appropriate error code and records a metric. Outline how you would run this test reliably in CI.

HardTechnical

77 practiced

Design and implement automated tests to validate idempotency and concurrency behavior for a payment processing API. Your tests should attempt to create duplicate payments via simultaneous requests using the same idempotency key and verify that only one charge is created. Describe how you would reproduce race conditions, validate database state, and keep tests deterministic.

HardSystem Design

50 practiced

Design an automated security testing workflow that orchestrates reconnaissance, automated authentication checks, injection attack simulation, data exfiltration checks, and report generation. Include integration points for SAST, DAST, runtime sensors, and manual penetration testing results. Describe how this pipeline fits into PR gating and nightly security scans while avoiding developer disruption.

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