Interview-Ready Unit Tests: Input Validation, Edge Cases, and Structure | MockRounds

Hiring teams watch how you design tests to expose bugs, not just whether code runs.

In this short session, you’ll tackle rapid-fire questions on writing and organizing unit tests for functions—especially input validation and edge cases—then we reveal answers with concise tips you can reuse in interviews.

Quiz link: https://mockrounds.com/security_testi...

Start from the contract: name tests by behavior (function_whenCondition_shouldOutcome) and cover happy path plus boundaries.
Validate inputs first: exercise min/max, empty/blank, null/undefined, zero/negative, large sizes, Unicode/locale, and malformed types.
Prefer table-driven cases for combinatorics; add property-based or fuzz checks where it makes sense, keeping seeds for reproducibility.
Keep logic isolated: mock I/O, time, and randomness behind interfaces; don’t over-mock—assert behavior, not calls, unless integration is the goal.
Organize with Arrange-Act-Assert; use small fixtures/factories; separate unit vs integration; run fast tests locally and tag slow ones for CI.

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