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Test migrations: 3 sourced coding agent stories

Moving a test suite from one framework to another, such as Enzyme to React Testing Library or JUnit 3 to JUnit 4. Of the 3 stories, 1 was published by a tool vendor and 2 by the people who did the work. 3 involve an existing codebase and 0 started from scratch. Every number links to where it was published.

• Vendor-published Test migration brownfield

  Asana finishes a five-year Enzyme → React Testing Library migration in two weeks with Codex

  Asana · 2026-08-19

  • ~2 weeks Calendar time
  • ~1.5 weeks Engineering effort
  • Up to 4 Parallel agents

  OpenAI Codex

• Practitioner (own blog/paper) Test migration brownfield

  Airbnb migrates ~3.5K Enzyme test files to React Testing Library in 6 weeks with LLMs

  Airbnb · 2025-03

  • ~3,500 Test files migrated
  • 6 weeks Actual duration
  • 1.5 years of engineering time Manual estimate

  Various tools

• Practitioner (own blog/paper) Test migration brownfield

  Google migrates 5,359 test files from JUnit3 to JUnit4 in 3 months with LLMs

  Google · 2025-01

  • 5,359 Files migrated
  • 149,000+ Lines modified
  • 3 months Duration

  Google internal migration toolkit (fine-tuned Gemini)