Buglyst Blog
Learn to debug under pressure.
Playbooks for fast pattern recognition, guides for the full investigation, and articles for the engineering judgment around the edges.
17 playbooks · 509 guides · 95 articles · 12 linked practice labs ·skip to practice
Fast pattern recognition for the production failures engineers see most often.
17 playbooks
Debugging Env Var Issues
A concise checklist for incidents where local works but CI, staging, or production changes behavior.
Debugging Cache Stampedes
How to recognize and contain request spikes when cached data expires.
Debugging CORS Origin Bugs
A practical way to inspect origin parsing, credentials, and header behavior.
Debugging Retry Bugs
Retry issues often hide the first failure and create duplicate work.
Debugging Timezone Bugs
Time bugs usually live at day boundaries, DST changes, and unit conversions.
Debugging Pagination Bugs
Pagination bugs hide in boundary math, cursor reuse, and new records arriving between pages.
Structured investigations for the failure modes engineers meet in real systems.
Jest Module Mock Not Working: A Debugging Guide
A practical debugging guide for when Jest's jest.mock() doesn't actually mock the module, covering hoisting issues, path mismatches, and module caching.
Jest Fake Timers Not Advancing — Why setTimeout/setInterval Never Fire
A firefighting guide for when Jest's fake timers stall — timers don't advance, tests hang, or assertions time out. Covers the real root causes like legacy vs modern timer API, async gaps, and jest.useFakeTimers() placement.
Jest Async Test Timeout Exceeded: Root Causes and Debugging Steps
A practical guide to diagnosing and fixing Jest async test timeouts, covering promise hanging, done() misuse, and timeout configuration.
Vitest Coverage Not Collecting: Debugging Empty or Missing Coverage Reports
A direct guide to diagnosing why Vitest coverage reports come empty or missing, with concrete commands, config checks, and a real incident walkthrough.
Playwright Locator Not Found: Selector Timeout & Element Resolution
Diagnose and fix Playwright's 'locator not found' error with concrete debugging steps, common causes, and a production war story.
Playwright route.intercept Not Working: Silent Failures and Missing Requests
When route interception silently fails in Playwright, requests pass through unmodified. This guide covers real causes: glob patterns, method scope, page lifecycle, and route handler ordering.
Long-form thinking on debugging habits, observability, and the systems around the bug.
Debugging CSS Layout Issues: A Systematic Approach to Fixing Broken Layouts
A practical, step-by-step system for diagnosing and fixing CSS layout bugs — from overflow and collapsing margins to flexbox and grid misbehavior. Includes real DevTools workflows and a war story from production.
Debugging Accessibility Violations: A Systematic Approach from Audit to Fix
A practical guide to identifying, triaging, and fixing accessibility violations in web applications, covering automated tools, manual testing techniques, and common pitfalls.
Find the Real Cause of a Slow Page: A Profiling Protocol for Engineers
A practical protocol for profiling web page performance — not a list of metrics, but a repeatable process for finding what actually slows down your users.
Tracking Down Memory Leaks in Browser JavaScript: A Practical Field Guide
Memory leaks in the browser are subtle and hard to reproduce. This guide covers practical techniques to detect, isolate, and fix them using Chrome DevTools, heap snapshots, and allocation timelines.
Why Your 60fps Animation Stutters: A Deep Dive Into the Browser Event Loop
The event loop isn't just about callbacks. It's about when and in what order the browser processes tasks, microtasks, and rendering. Here's what actually happens between frames.
Remote Debugging Mobile Devices at Scale: What Works and What Doesn't
Setting up remote debugging for iOS and Android devices involves more than just enabling Developer Mode. Here's what I've learned from debugging over 500 devices in production.