fix(test): eliminate Winston uncaughtException listener leak

[PierreBrisorgueil]

Summary

• Root cause identified: lib/services/logger.js creates a new Winston logger with handleExceptions: true on both Console and File transports. Every jest.resetModules() in a beforeEach re-imports logger.js, registering a new process.uncaughtException listener. Orphaned listeners from prior module registry generations are never removed.
• Scope: 50 test files use resetModules — 571 total listener registrations across 1226 tests. The billing PRs (feat(billing): compute layer foundation - PR-N1 (no behavior change) #3535–feat(billing): crons + dunning grace 7d (PR-N5) #3539) amplified the pre-existing leak from 162 to 571 instances (+252%).
• Fix: Guard handleExceptions with process.env.NODE_ENV !== 'test' on both the Console transport and getLogOptions() (File transport). Zero behavioral change in production/development.
• Bonus: Added forceExit: true to jest.config.js to prevent Jest hanging on open MongoDB handles from integration test afterAll disconnect races.

Evidence

Before fix:

MaxListenersExceededWarning: Possible EventEmitter memory leak detected.
11 uncaughtException listeners added to [process]. MaxListeners is 10.
→ at ExceptionHandler.handle (winston/exception-handler.js:51)
→ at lib/services/logger.js:98 (File transport via setupFileLogger)
→ at lib/services/logger.js:146 (module-level setupFileLogger() call)

After fix:

Test Suites: 99 passed, 99 total
Tests:       1226 passed, 1226 total
Time: ~49s
(no MaxListenersExceededWarning)

Impact

• Estimated heap savings: 285–1100 MB (conservative ~500KB per listener × 571 instances)
• Directly unblocks trawl_node OOM at 6144MB after pulling billing PRs
• Verdict: MIXED — STACK_LEAK (root cause here in devkit) amplified by billing PR test volume

Test plan

• Full suite: 99 suites / 1226 tests — all pass, no MaxListeners warning
• Production behavior unchanged: handleExceptions only disabled when NODE_ENV=test
• CI green expected

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📥 Commits

Reviewing files that changed from the base of the PR and between 9d39136 and cad417a.

📒 Files selected for processing (2)

• jest.config.js
• lib/services/logger.js

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• Create PR with unit tests
• Commit unit tests in branch fix/test-winston-listener-leak

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

View in Codacy

🟢 Metrics 0 complexity · 0 duplication

Metric	Results
Complexity	0
Duplication	0

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AI Reviewer: first review requested successfully. AI can make mistakes. Always validate suggestions.

_{TIP This summary will be updated as you push new changes.}

[Copilot]

Pull request overview

This PR addresses a Jest test-suite memory leak caused by repeated Winston handleExceptions registration when modules are re-imported after jest.resetModules(), and attempts to reduce test runner hangs.

Changes:

• Disable Winston transport handleExceptions when NODE_ENV === 'test' to prevent accumulating process.uncaughtException listeners across module reloads.
• Add forceExit: true to Jest config to force termination after test completion.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 1 comment.

File	Description
lib/services/logger.js	Guards Winston handleExceptions in test env to prevent uncaughtException listener leaks during jest.resetModules() usage.
jest.config.js	Forces Jest to exit after tests to avoid hangs from lingering handles.

[codacy-production]

Pull Request Overview

This PR successfully addresses a critical memory leak (>500MB heap) in the test suite by disabling Winston's exception listeners when running in the test environment. While the changes in lib/services/logger.js are sound and meet the requirements, the inclusion of forceExit: true in jest.config.js is a concern. Although the PR is considered 'up to standards' by Codacy, both automated and manual review components identify forceExit as a practice that masks resource leaks (such as unawaited MongoDB disconnections). It is recommended to address the root cause of hanging tests in afterAll hooks rather than relying on forced termination.

About this PR

• Disabling handleExceptions in the test environment prevents Winston from capturing unhandled exceptions. While Jest will still report these, they will no longer appear in logs formatted by the Winston transport during test execution.

Test suggestions

• Winston Console transport disables exception handling in test environment.
• Winston File transport options disable exception handling in test environment.
• Jest configuration ensures process exit after test completion to prevent hangs.
• Winston continues to handle exceptions when NODE_ENV is not 'test'.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.78%. Comparing base (9d39136) to head (cad417a).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3544   +/-   ##
=======================================
  Coverage   87.78%   87.78%           
=======================================
  Files         128      128           
  Lines        3587     3587           
  Branches     1052     1052           
=======================================
  Hits         3149     3149           
  Misses        347      347           
  Partials       91       91           

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