fix(cli): reset themeManager between tests to ensure isolation

[NTaylorMullen]

Summary

Fixes non-deterministic SVG snapshot failures in the CLI package by ensuring that themeManager state (active theme and terminal background) is reset between every test run.

Details

Commit f9f916e1d enabled 24-bit color in tests and introduced SVG snapshots via toMatchSvgSnapshot. Since themeManager is a global singleton and Vitest reuses worker processes, state from one test (e.g., setting a terminal background or active theme) would leak into subsequent tests. This led to non-deterministic hex code mismatches in SVG snapshots (e.g., #3d3f51 vs #45475a).

This PR adds a beforeEach hook to packages/cli/test-setup.ts to reset themeManager to its default state before every test.

Related Issues

Fixes the failures reported in the Gemini CLI Maintainers chat thread.

How to Validate

1. Created a reproduction test file packages/cli/src/ui/themes/leak.test.ts that explicitly modified themeManager in one test and verified the leak in the next.
2. Confirmed the leak existed before the fix.
3. Confirmed the leak was eliminated after applying the fix to test-setup.ts.
4. Verified that all existing CLI tests (npm test -w @google/gemini-cli) continue to pass (barring pre-existing failures on main).

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run

---

Update: Added themeManager.clearFileThemes() and ensured all theme clearing methods (clearExtensionThemes, clearFileThemes, loadCustomThemes({})) are called in test-setup.ts for complete isolation, per code review feedback.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves an issue where test state was leaking between runs, leading to non-deterministic SVG snapshot failures. By introducing a reset mechanism for the themeManager before each test, it ensures proper test isolation and reliability, preventing color mismatches in visual tests.

Highlights

• Test Isolation: Implemented a beforeEach hook in packages/cli/test-setup.ts to reset the themeManager's state, including custom themes, active theme, and terminal background, before each test run.
• Fix for Non-Deterministic Failures: Addressed non-deterministic SVG snapshot failures in the CLI package caused by state leakage from the global themeManager singleton between Vitest worker processes.

Changelog

• packages/cli/test-setup.ts
  • Imported themeManager and DEFAULT_THEME to enable state management.
  • Added a beforeEach hook to reset themeManager's state to its defaults before each test.

Activity

• A reproduction test file (packages/cli/src/ui/themes/leak.test.ts) was created to explicitly demonstrate the themeManager state leak.
• The existence of the leak was confirmed prior to the fix.
• The leak was verified to be eliminated after applying the fix in test-setup.ts.
• All existing CLI tests were validated to ensure they continue to pass.

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[gemini-code-assist]

Code Review

This pull request addresses non-deterministic test failures by resetting the themeManager state in a beforeEach hook. The change is correct in principle, but it's incomplete as it misses resetting themes loaded from extensions, which could lead to continued state leakage between tests. I've added a suggestion to call themeManager.clearExtensionThemes() to ensure complete test isolation.

[github-actions]

Size Change: +900 B (0%)

Total Size: 25.8 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	25.3 MB	+900 B (0%)
./bundle/node_modules/@google/gemini-cli-devtools/dist/client/main.js	221 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/_client-assets.js	227 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/index.js	11.5 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/types.js	132 B	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B
./bundle/sandbox-macos-strict-open.sb	4.82 kB	0 B
./bundle/sandbox-macos-strict-proxied.sb	5.02 kB	0 B

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