You are assigned to refactor a legacy module with incomplete documentation and no unit tests. How would you approach this task to minimize risk and improve maintainability?

Use the CIRCLES framework: Clarify scope, Investigate current behavior, Recommend incremental refactor steps, Communicate plan to stakeholders, Listen for feedback, Execute with CI/CD, Summarize impact. Step‑by‑step: 1) Map critical paths via static analysis, 2) Write smoke tests for observable outputs, 3) Add unit tests for isolated functions, 4) Refactor small, test‑driven chunks, 5) Update documentation, 6) Conduct code reviews, 7) Monitor post‑deployment metrics.

I would start by clarifying the module’s responsibilities and identifying the most critical use cases. Using static analysis tools I’d map out the call graph and locate the entry points that affect production traffic. Next, I’d write smoke tests that capture the current observable behavior, ensuring that any change does not break existing functionality. With those tests in place, I’d incrementally add unit tests for each function, aiming for at least 80% coverage. Refactoring would then proceed in small, test‑driven chunks, each reviewed by peers and integrated into the CI pipeline. Throughout the process I’d maintain clear documentation of the changes and communicate progress to stakeholders. After deployment, I’d monitor key metrics—latency, error rates, and test coverage—to confirm that the refactor delivered tangible improvements while preserving stability.