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.
HardSystem Design
0 practiced
Design a test and verification strategy to detect edge-case regressions for a multi-region microservice deployed in three regions, running mixed languages (Java and Node). The service processes user-uploaded files and performs validation and transformation. Requirements: catch edge cases including file-size limits, partial uploads, network partitions, locale encodings, and GC pauses. Describe mocks, synthetic traffic, end-to-end tests, integration tests, canary rollout checks, and how to automate these in CI without excessive cost.
MediumTechnical
0 practiced
Binary search is simple but prone to subtle bugs. Enumerate edge cases you would test for a classic binary_search(arr, target) implementation: empty array, one element, two elements, target at boundaries, not present, repeated elements, and mid calculation overflow. Provide specific inputs that would reveal a bug if mid is computed as (low+high)/2 in a 32-bit signed integer implementation.
MediumTechnical
0 practiced
Design a fuzz testing strategy for an image decoder. Explain corpus selection, mutation strategies, grammar-awareness vs blind mutation, crash triage, coverage metrics to drive fuzzing, and how to integrate sanitizers and minimizers. How would you ensure your fuzzing finds deep edge cases and not just trivial parse errors?
MediumTechnical
0 practiced
Design property-based tests for a banking transaction system where operations include deposit(amount), withdraw(amount), and transfer(from, to, amount). List invariants to assert (e.g., no negative balances, conservation of total balance when transfers occur) and describe how to generate sequences of operations that capture edge cases like overdrafts, zero amounts, and concurrent transfers.
MediumTechnical
0 practiced
Implement a robust integer parser safeParseInt(String s) in Java that handles leading/trailing whitespace, optional '+'/'-' signs, empty or null inputs, non-digit characters, and detects 32-bit integer overflow without relying on BigInteger. Before coding, list the edge-case tests you would write and the behavior (e.g., return Optional.empty() or throw NumberFormatException).
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