Agentic Playwright testing with Nix

Sat, 15 Aug 2026 21:31:07 +0200

I don’t do much front-end web development these days, but I enable people who do.

I use a lot of coding agents for my daily work with back-end APIs and service meshes.

I’ve known for a long time that agentic workflows instrumenting Playwright to run headless browser tests based on prompts has advanced quite a lot. I just haven’t got around to try it out.

tl;dr ¶

Playwright, its browsers and its MCP server are all in nixpkgs. No package.json, no npm install, no npx playwright install.
nixpkgs’ playwright-test hardcodes the full browser set into its wrapper, so the naive setup drags 2.2 GB of Chromium, Firefox and WebKit into your devshell whether you want them or not. I managed to push that down to 634 MB.
Headed Chromium and interactive debugging lives behind a flake-parts partition.
The planner/generator/healer agents run on an existing Claude Code session.
I practice TDD workflows for writing end-to-end tests.

The application under test ¶

The thing I’m practising on is a generic client area dashboard for a software service, written in Rust on topcoat with toasty. So I’m doing three things here: Testing topcoat, toying around with client dashboards, and getting my agentic playwright testing workflow up.

Agentic on Simon Shine

Agentic Playwright testing with Nix

tl;dr ¶

The application under test ¶