Writing

Notes from the work: what we learned building testing tools and fixing test suites. Articles are published on dev.to/stevez, with earlier notes on Medium.

Code coverage for Next.js — a series

How to measure what your end-to-end tests actually cover, and why it's harder than it looks in Next.js.

1. nextcov — Collecting Test Coverage for Next.js Server Components Coverage for server components from Playwright tests, and how nextcov collects it.
2. Why Istanbul Coverage Doesn't Work with Next.js App Router The instrumentation approach most teams reach for first — and where it breaks.
3. V8 Coverage vs Istanbul: Performance and Accuracy A side-by-side comparison of the two coverage engines.
4. V8 Coverage Limitations and How to Work Around Them The blind spots in V8 coverage and practical workarounds.
5. How to Merge Vitest Unit, Component, and E2E Test Coverage One coverage report across every kind of test.
6. E2E Coverage in Next.js: Dev Mode vs Production Mode Which build to measure, and why the numbers differ.

Reliable Playwright tests

• Parallel, isolated Playwright mocks with msw-terrarium Stateful API mocks that let tests run in parallel without interfering.
• From 1.2GB to 24MB: How I Sped Up Our Next.js CI/CD Pipeline by 4× in One Afternoon A real-world CI speed-up, step by step.

Earlier testing notes

• Testing NextJS Server Side Rendering with Playwright
• How to mock Javascript class constructor in Jest
• Simulating CRUD operations with json-server and In-memory data

Browser automation & AI

• playwright-repl: Browser Automation From Your Terminal, No Code Required
• I Put Playwright Inside a Chrome Side Panel — Console, Recorder, and Debugger Included
• I Built a VS Code Extension That Turns Playwright Into an Interactive REPL
• Let AI Control Your Real Browser — Not a Throwaway One
• How Fast Can Browser Automation Be? I Benchmarked 3 Approaches

Want this kind of care applied to your test suite?

Book a 30-min call · or email steve.zhang@intelliz.io