Edge Case Identification and Testing Questions

Focuses on systematically finding, reasoning about, and testing edge and corner cases to ensure the correctness and robustness of algorithms and code. Candidates should demonstrate how they clarify ambiguous requirements, enumerate problematic inputs such as empty or null values, single element and duplicate scenarios, negative and out of range values, off by one and boundary conditions, integer overflow and underflow, and very large inputs and scaling limits. Emphasize test driven thinking by mentally testing examples while coding, writing two to three concrete test cases before or after implementation, and creating unit and integration tests that exercise boundary conditions. Cover advanced test approaches when relevant such as property based testing and fuzz testing, techniques for reproducing and debugging edge case failures, and how optimizations or algorithmic changes preserve correctness. Interviewers look for a structured method to enumerate cases, prioritize based on likelihood and severity, and clearly communicate assumptions and test coverage.

HardTechnical

0 practiced

Design an automated test framework for stateful workflows that include external side effects (HTTP callbacks, email, DB writes). The framework must enumerate edge cases such as duplicate callbacks, delayed responses, partial failures, and retries. Explain how you'd use mocking, contract tests, end-to-end verification, and replayable traces to ensure correctness and idempotency.

MediumSystem Design

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Design a test harness and strategy to validate idempotency guarantees for a REST payment endpoint: include deterministic integration tests that replay requests, simulate partial failures in downstream services, use mocks for payment provider behavior, and show how you'd assert exactly-once effects across retries and concurrent clients.

MediumTechnical

0 practiced

Production shows steadily increasing memory usage only under heavy traffic. Describe a step-by-step plan to reproduce and debug the memory leak in staging/local, including load patterns to use, tools to capture heapdumps or pprof profiles, deterministic ways to trigger growth, and how you'd add regression tests to prevent reintroduction.

MediumTechnical

0 practiced

A service accepts numeric strings over JSON and protobuf endpoints. Explain a test plan to detect integer overflow and precision loss across transport and language boundaries, including malformed encodings, extremely large BigInt values, and float rounding during serialization/deserialization. Include cross-language test matrices.

MediumTechnical

0 practiced

Your HTTP microservice supports pagination via `page` and `limit`. Enumerate edge cases: limit=0, negative page, very large limit, offset overflow, concurrent data changes during pagination, missing params, last partial page. For each case, propose unit and integration tests and a performance test that validates resource usage when extreme parameters are used.

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