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Openai·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Apr 2026Remote

Summary

Interviewed at OpenAI for a software engineering role and got a refactoring question, which sounds easy until you're actually sitting there trying to decide how much to change without breaking the spirit of the original code.

Questions Asked (1)

Q1

Given a working but poorly written code snippet with long functions, unclear variable names, and no tests, refactor it to improve readability, modularity, and testability. Add helper functions, rename variables, and write unit tests.

Technical Trade-offsSystem DesignAlgorithms & Data Structures
Author's notes

I spent the first few minutes just reading the code and honestly second-guessing whether I should rename everything or stay conservative.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the code's purpose and identifying pain points, then refactor incrementally with tests to ensure behavior preservation. Focus on extracting small, single-responsibility functions, renaming for clarity, and adding unit tests that cover edge cases.

Pro tip: Before refactoring, write characterization tests to lock in current behavior, then improve the code under that safety net. This demonstrates professional discipline and reduces risk.

1. Understand and Document

Read the code, identify its inputs, outputs, and side effects. Write a brief summary of what it does and note any unclear or risky parts.

2. Add Characterization Tests

Write tests that capture the current behavior of the code, including edge cases, to ensure refactoring doesn't break functionality.

3. Refactor Incrementally

Extract helper functions for distinct logical blocks, rename variables and functions to be descriptive, and reduce function length. Run tests after each small change.

4. Improve Testability

Decouple dependencies (e.g., via dependency injection) and ensure functions are pure where possible. Add unit tests for new helper functions.

5. Review and Validate

Review the refactored code for readability and modularity. Ensure all tests pass and consider adding integration tests if needed.

Key Points to Mention

  • Behavior preservation: refactoring should not change external behavior.
  • Single Responsibility Principle: each function should do one thing.
  • Meaningful naming: variables and functions should reveal intent.
  • Test coverage: unit tests for helpers and edge cases.
  • Incremental refactoring: small, safe steps with frequent test runs.
  • Dependency injection: to make code more testable and modular.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.