Run the unit tests in Chromium instead of jsdom

.github/workflows/test.yml

@@ -17,10 +17,7 @@ jobs:
 
       - uses: pnpm/action-setup@v4
 
-      # Node 22, not 20: jsdom 30 pulls in undici, which reads
-      # `markAsUncloneable` off node:worker_threads unconditionally. That only
-      # exists from Node 22.10, so on Node 20 every jsdom test worker dies at
-      # startup with "[vitest-pool]: Failed to start forks worker".
+      # Vite 8 requires ^20.19.0 || >=22.12.0.
       - name: Setup Node.js environment
         uses: actions/setup-node@v4
         with:
@@ -33,6 +30,10 @@ jobs:
       - name: Build package
         run: pnpm run build
 
+      # The unit tests run in a real Chromium through Vitest browser mode.
+      - name: Install Playwright Chromium
+        run: pnpm exec playwright install --with-deps chromium
+
       - name: Test
         run: pnpm run test
 

.gitignore

@@ -7,3 +7,5 @@ playwright-report
 coverage
 
 storybook-static
+.vitest-attachments
+test/__screenshots__

.prettierignore

@@ -4,3 +4,5 @@ pnpm-lock.yaml
 test-results
 playwright-report
 coverage
+.vitest-attachments
+test/__screenshots__

README.md

@@ -644,17 +644,17 @@ That serves an index of every demo; each one is also reachable directly at `?dem
 ## Testing
 
 ```bash
-pnpm test         # Vitest: the state machine, in jsdom and in SSR
+pnpm test         # Vitest: the state machine, in Chromium and in SSR
 pnpm run test:coverage
-pnpm run test:e2e  # Playwright: real browsers, across Chromium, Firefox and WebKit
+pnpm run test:e2e  # Playwright: the app, across Chromium, Firefox and WebKit
 ```
 
+Both suites need a browser. Install them once with `pnpm exec playwright install chromium firefox webkit`.
+
 The e2e suite serves the playground on port 5173. If that port is already taken — Vite's default, so it often is — set `PLAYWRIGHT_PORT` to something free, otherwise Playwright reuses whatever is already listening there and every test times out:
 
 ```bash
 PLAYWRIGHT_PORT=5199 pnpm run test:e2e
 ```
 
-Browsers are installed separately, once: `pnpm exec playwright install chromium firefox webkit`.
-
-Vitest covers the engine's own logic. Playwright covers everything jsdom cannot reach: real animation interpolation through the Web Animations API, real `IntersectionObserver` for `inView`, real pointer input for `hover`/`press`, and real scrolling for `useScroll`.
+Vitest runs the unit tests in a real Chromium through browser mode, so they get real animation interpolation, a real `IntersectionObserver` and real computed styles. Playwright drives the whole playground app instead, across three engines.

e2e/diagnostics.spec.ts

@@ -3,8 +3,8 @@ import {expect, test} from "@playwright/test"
 /*
 Solid 2 reports reactivity mistakes as dev-mode console diagnostics rather than
 as failures — an unowned effect, a flush that is a silent no-op, a top-level
-prop read that will never update. None of those surface in jsdom or in an
-assertion, so this walks every playground demo in a real dev build and fails on
+prop read that will never update. None of those surface as an assertion
+failure, so this walks every playground demo in a real dev build and fails on
 any of them.
 
 The demo list is scraped from the playground's own index page rather than

package.json

@@ -63,11 +63,11 @@
 		"@types/node": "^22.12.0",
 		"@typescript-eslint/eslint-plugin": "^6.17.0",
 		"@typescript-eslint/parser": "^6.17.0",
+		"@vitest/browser-playwright": "4.1.11",
 		"@vitest/coverage-v8": "^4.1.11",
 		"eslint": "^8.56.0",
 		"eslint-plugin-eslint-comments": "^3.2.0",
 		"eslint-plugin-no-only-tests": "^3.1.0",
-		"jsdom": "^30.0.1",
 		"prettier": "^3.1.1",
 		"solid-js": "2.0.0-rc.5",
 		"storybook": "^10.6.0",