test: scaffold regression test suite for React 17 upgrade (WIP)

[bosun-ai]

Summary

Prepare upgrade path for React 17 by introducing a basic regression test suite scaffold and associated tooling. This PR is a work in progress and serves as a placeholder for the React 16.8.6 → 17.0.2 upgrade effort.

Changes

• Added regression test suite scaffolding under regression-tests/:
  • jest.config.js with jsdom environment and setup file
  • setupTests.js configuring @testing-library, MSW server lifecycle, and a fetch polyfill
  • server.js and handlers.js for MSW request mocking
  • simple-component.test.js example rendering and click interaction test
• Introduced test dependencies:
  • @testing-library/react@12.1.5
  • @testing-library/jest-dom@4.2.4
  • msw@0.25.0
  • cross-fetch@^4.1.0 (Node fetch polyfill for tests)
• Added test:regression script to package.json invoking Jest with the regression config
• Added .nvmrc specifying Node 12 for consistent local/test environment

Reasoning

• Establish a minimal regression test framework to validate UI behavior during React version upgrades.
• Use MSW to isolate tests from real network calls and ensure deterministic behavior.
• Provide a consistent Node version via .nvmrc to reduce environment-related test variance.

Regression test suite setup

• Test framework
  • Jest with jsdom test environment configured via regression-tests/jest.config.js
  • @testing-library utilities for DOM queries and events
  • MSW for request mocking, with lifecycle managed in setupTests.js
  • Cross-fetch polyfill for Node environment
• File locations
  • Config: regression-tests/jest.config.js
  • Setup: regression-tests/setupTests.js
  • MSW server: regression-tests/server.js
  • Handlers: regression-tests/handlers.js
  • Example test: regression-tests/simple-component.test.js

Testing instructions

• Run regression tests:

  nvm use && yarn run test:regression
  

• Example single-component test run:

  nvm use && yarn run test:regression
  

  Note: Jest will discover tests matching **/*.test.js under regression-tests/.

Impact and risk

• Low risk: changes are test-only scaffolding and do not modify application runtime code.
• Ensures a baseline test suite exists before proceeding with React upgrade changes.

Follow-ups / open questions

• Expand test coverage to include key components and interaction patterns affected by React 17 changes (event system, rendering, portals).
• Confirm Node version alignment with CI and production; adjust .nvmrc as needed.
• Integrate regression tests into CI (e.g., a dedicated job).
• Define MSW handlers for endpoints used by components under test.

Reviewer checklist

• Validate that yarn run test:regression executes successfully locally with nvm use.
• Confirm the chosen dependency versions are compatible with React 16.8.6 and 17.0.2 during the upgrade.
• Suggest additional components or flows to prioritize for regression coverage.

Links

• This is a test PR for the React upgrade effort; do not merge.

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This pull request is created by bosun, a code maintenance automation platform. For more information, visit bosun.ai.