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.
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Structured investigations for the failure modes engineers meet in real systems.
Debugging Cypress Tests Inside an iFrame: The Cross-Origin Trap
A practical debugging guide for when Cypress tests fail inside iframes—covering cross-origin restrictions, timing issues, and element access.
Cypress intercept stub not intercepting requests — debugging guide
A debugging guide for when cy.intercept() stubs silently fail to match or intercept requests, covering URL patterns, method mismatches, timing, and aliasing traps.
React Testing Library fireEvent Not Triggering: Silent Failures and Real Fixes
When React Testing Library's fireEvent doesn't trigger, it's usually due to stale closures, wrong event type, or async state updates. This guide covers real causes and fixes.
MSW Request Not Intercepted: Why Your Handler Isn't Catching the Call
A practical guide to debugging why MSW (Mock Service Worker) handlers fail to intercept requests, covering worker registration, URL mismatches, and lifecycle issues.
Jest Fake Timers Not Working: A Debugging Guide
A practical guide to debugging when Jest's fake timers (jest.useFakeTimers) don't behave as expected—covering async race conditions, timer scope, and common pitfalls.
Debugging Testcontainers Container Startup Timeout
A focused guide for diagnosing and fixing Testcontainers startup timeouts, covering Docker resource constraints and Ryuk issues.
Long-form thinking on debugging habits, observability, and the systems around the bug.
How to Reproduce a Flaky Test: From CI Logs to Reliable Failure
A practical guide to turning intermittent test failures into reliably reproducible bugs, with techniques ranging from loop testing to thread sanitizers.
Property-Based Testing: Finding the Off-by-One That Lived in Production for 18 Months
A concrete story of how switching from example-based tests to property-based tests caught a timing bug that had survived code review, QA, and 18 months of production traffic.
How We Reduced End-to-End Test Flakiness by 80% with Deterministic Seeding
After months of chasing intermittent failures in our CI pipeline, we implemented a three-part strategy — deterministic seeding, isolated state per test, and a structured retry budget — that cut flaky end-to-end test failures by 80%.
Snapshot Testing: The 5 Hidden Failure Modes That Will Break Your CI
Snapshot tests seem like a safety net, but they often hide real bugs, bloat diffs, and silently break your CI. Here are the five failure modes I've seen in production and how to fix them.
Testing Async Code: Avoiding Flakiness and False Positives in JavaScript
Async testing is full of traps: unhandled rejections, race conditions, and tests that pass when they shouldn't. Here's how to write reliable async tests in JavaScript.
Testing Error Handling Code Paths: A Practical Approach
Error handling code is often the least tested and most brittle. Here's how to cover those paths with fault injection, mocks, and chaos engineering.