← Bilt Rewards Interview Insights
The three tests were around restaurant triple-points logic, a missing merchant code case, and daily points aggregation.
Start by running the tests to see the failures, then read the stack traces and test code to identify the root cause of each failure. Prioritize fixes that are minimal and localized, ensuring you don't break other tests. Walk through each failure methodically, explaining your reasoning and the trade-offs of your chosen fix.
Pro tip: Before changing any code, reproduce the failures locally and use a debugger or print statements to confirm your hypothesis about the root cause. This prevents guesswork and demonstrates a disciplined debugging approach.
Run the failing tests to see the exact errors and stack traces. Note which assertions fail and what the expected vs. actual values are.
For each failure, trace from the test assertion back to the production code. Identify the specific line or logic error causing the mismatch.
Determine the smallest change that corrects the behavior without altering unrelated functionality. Consider if the fix should be in the test, but since tests are fixed, focus on production code.
Apply the fix, then rerun all tests to ensure the target test passes and no regressions occur. If multiple failures, fix one at a time and verify after each.
Discuss why your fix is minimal, any potential side effects, and alternative approaches you considered but rejected.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Talked about edge-case tests for null and empty inputs, input validation closer to the entry point, and a code review checklist for things like string comparisons and loop boundaries.
Start by briefly summarizing the root cause of the bugs you fixed, then pivot to a layered prevention strategy that combines automated tests, process improvements, and monitoring. Emphasize that prevention is about building systems and culture, not just adding tests, and tailor your answer to the specific context of the bugs (e.g., edge cases, integration points, or missing validation).
Pro tip: Show maturity by acknowledging that not all regressions can be prevented, so you also invest in fast detection and rollback mechanisms. Mention that you'd track the effectiveness of your prevention measures (e.g., regression rate) to continuously improve.
Explain what specifically allowed the bug to slip through (e.g., missing test coverage, unclear requirements, or lack of integration testing). This shows you understand the problem deeply before proposing solutions.
Propose writing unit, integration, or end-to-end tests that reproduce the bug and cover the edge cases. Mention that these tests should be added to the CI pipeline to run on every change.
Suggest process changes such as mandatory test coverage for bug fixes, peer review checklists, or pair programming on complex areas. This addresses the human factors that contributed to the regression.
Describe how you would add logging, metrics, or alerts to detect similar issues in production quickly. This ensures that if a regression does occur, it's caught before impacting users.
Mention conducting a blameless post-mortem and sharing findings with the team. Also, track the effectiveness of the prevention measures and adjust as needed.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.