test: Improve debounce/throttle test performance by replacing real timers with fake timers

[miinhho]

Summary

Replaced real timer usage with fake timers in debounce and throttle tests to eliminate flaky test risks and significantly improve test execution time.

Problem

• Tests were using real timers with delay() function, making them slow and potentially flaky
• Real timer-based tests are susceptible to timing issues in CI environments
• Total test execution time was unnecessarily long due to actual time delays

Solution

• Targeted approach: Only replaced real timers with fake timers for debounce and throttle tests that were the primary cause of slow test execution
• Simple replacements: For straightforward cases, replaced delay() calls with vi.advanceTimersByTime() for precise time control
• Preserved complex tests: When tests required additional modifications beyond simple delay() replacement, maintained original tests using vi.useRealTimers() to avoid breaking existing functionality

Performance Improvements

Individual Test Files

Test File	Before	After	Improvement
src/compat/function/debounce.spec.ts	4.08s	1.16s	3.52x faster
src/compat/function/throttle.spec.ts	5.08s	2.02s	2.52x faster
src/function/debounce.spec.ts	903ms	12ms	75.25x faster
src/function/throttle.spec.ts	1.45s	15ms	96.67x faster

Overall Test Suite Impact

Test execution time: 19.64s → 11.33s (42.3% improvement)

Benefits

• Eliminated flaky test risks - No dependency on system timing
• Faster CI/CD pipeline - Reduced test execution time by 42%
• More reliable tests - Deterministic timing behavior

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Preview	Comments	Updated (UTC)
es-toolkit	Ready	Preview	Comment	Nov 18, 2025 0:58am

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.97%. Comparing base (8beb7a3) to head (486cb92).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1359   +/-   ##
=======================================
  Coverage   99.97%   99.97%           
=======================================
  Files         468      468           
  Lines        4459     4459           
  Branches     1313     1313           
=======================================
  Hits         4458     4458           
  Misses          1        1           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.