test: fix fork-worker process-listener leaks behind the windows CI flake (#159)

[debugmcpdev]

Fixes #159.

Root cause

The failed run (28960586768 attempt 1) reported 157 passed | 2 skipped (160) files and 2462 passed | 5 skipped (2505) tests — exactly one file with exactly 38 tests never reported. The only 38-test file in the suite is tests/unit/proxy/dap-proxy-core.test.ts: its fork worker died before flushing results (unit project = pool: 'forks', isolate: true).

Why the fork died: the "registers handlers…" test spied process.on without mockImplementation, so the spy called through and setupGlobalErrorHandlers() attached 4 real listeners (uncaughtException, unhandledRejection, SIGTERM, SIGINT) to the vitest fork's process. afterEach only restored the spy — the listeners were never removed. The leaked uncaughtException handler runs errorShutdown().finally(() => process.exit(1)); after vi.resetAllMocks(), the captured shutdownFn returns undefined, so the handler either calls the real process.exit(1) or throws (.finally of undefined) — and a throw inside an uncaughtException handler is a fatal Node exit. Either way: [vitest-pool]: Worker exited unexpectedly, results lost, red CI over a green suite.

The same bug class was caught red-handed in the failed run's log for a second file — tests/unit/proxy/dap-proxy-dependencies.test.ts invokes the unhandledRejection handler (which schedules shutdownFn().finally(() => process.exit(1)) on the microtask queue) and restored the exit spy synchronously before it fired:

stderr | tests/unit/proxy/dap-proxy-dependencies.test.ts
[Test] UnhandledRejection: process.exit unexpectedly called with "1"

An audit found a third offender: tests/unit/cli/stdio-command.test.ts leaks real SIGTERM/SIGINT/exit listeners plus a 60s keepAlive interval per successful-start test.

Fix (no retries, no masking)

• tests/vitest.setup.ts — process-listener leak guard: baselines rawListeners for 8 critical events per fork, and after each test removes + loudly reports ([process-listener-leak], with test name + file) anything not in the baseline. LEAK_GUARD_STRICT=1 upgrades to a hard failure. Diagnostics handlers now include the test file path.
• tests/unit/proxy/dap-proxy-core.test.ts — capture handlers via mockImplementation (never attach); file-wide process.exit mock net (ProxyRunner.start() arms a real 10s setTimeout(() => process.exit(1))); inline exitSpy.mockRestore() calls removed so the net survives to restoreAllMocks.
• tests/unit/proxy/dap-proxy-dependencies.test.ts — settle the async exit chain before restoring the spy; assert shutdownFn + exit(1) (previously unasserted).
• tests/unit/cli/stdio-command.test.ts — capture process.on without attaching; drain the keepAlive interval via the captured SIGTERM handler; fake stdin everywhere (no more resume()/'end' listener on the fork's real stdin).
• tests/unit/proxy/proxy-manager-test-setup.ts — deleted (dead code; would have nuked vitest's own unhandledRejection handlers if ever imported).
• CI attribution — json reporter enabled on CI (written by the main process, so it survives fork death and records exactly which file never reported); test-results.json added to the windows-test-diagnostics artifact.

Failing-first proof

Guard landed before the test fixes flags exactly the killer (and the third offender):

[process-listener-leak] Removed leaked 'uncaughtException', 'unhandledRejection', 'SIGTERM', 'SIGINT'
listener(s) left by "ProxyRunner.setupGlobalErrorHandlers > registers handlers for uncaughtException,
unhandledRejection, SIGTERM, SIGINT" (tests/unit/proxy/dap-proxy-core.test.ts). ...

[process-listener-leak] Removed leaked 'SIGTERM', 'SIGINT', 'exit' listener(s) left by
"STDIO Command Handler > should start server successfully in stdio mode"
(tests/unit/cli/stdio-command.test.ts). ...   (×4 tests)

After the fixes, the same commands run clean under LEAK_GUARD_STRICT=1.

Verification

• LEAK_GUARD_STRICT=1 vitest run --project unit on all three fixed files — green, zero leak messages
• Full pnpm run test:ci-coverage (same command as the failing CI job) — green; full-output sweep: 0 [process-listener-leak] messages, 0 process.exit unexpectedly called messages (previously present), and the summary counts add up exactly (161+2 = 163 files, 2513+5 = 2518 tests — no lost workers)
• Stress loop on Windows (same platform as the flake): 30× the three fixed files under LEAK_GUARD_STRICT=1 — 30/30 green
• node scripts/flake-hunt.mjs 3 (within-file shuffle, fresh seeds) — 3/3 green
• Follow-up filed: Inject a process handle into ProxyRunner, setupGlobalErrorHandlers, and stdio-command signal registration #183 — DI process-handle injection for ProxyRunner/setupGlobalErrorHandlers/stdio-command

🤖 Generated with Claude Code

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