Migrating a suite

This page moves an existing Playwright suite to Pyro: install the package, rewrite the imports, point the runner at your config, update scripts and CI, then fix the first failures. Most suites need no changes beyond the imports. Plan time for re-baselining screenshots and for the behaviour differences.

1. Install

bun add --dev @povio/lightning-panda
# or
npm install --save-dev @povio/lightning-panda

The package bundles the browser for macOS 14+ (Apple silicon and Intel) and Linux x64 / arm64 with glibc 2.39+ (for example Ubuntu 24.04). There is no browser download step and no playwright install.

lightningpanda test runs your tests with bun test, so Bun must be on PATH even if the rest of your project uses Node. Check with bun --version. See Installation for platform details.

2. Rewrite the imports

Every import of @playwright/test, playwright, playwright/test and playwright-core becomes @povio/lightning-panda/playwright. Type-only imports change the same way.

import { test, expect } from '@playwright/test';             // before
import { test, expect } from '@povio/lightning-panda/playwright'; // after

import type { Page, Locator } from '@playwright/test';           // before
import type { Page, Locator } from '@povio/lightning-panda/playwright'; // after

import { chromium, devices } from 'playwright';                // before
import { chromium, devices } from '@povio/lightning-panda/playwright'; // after

This command rewrites them in place. It matches the module name only when it is the whole quoted string, so it works for import, import type, export ... from, import() and require(). It works with both BSD (macOS) and GNU tools because it uses Perl:

grep -rlE "['\"](@playwright/test|playwright/test|playwright-core|playwright)['\"]" \
    e2e playwright.config.ts \
  | xargs perl -pi -e 's{(["\x27])(?:\@playwright/test|playwright/test|playwright-core|playwright)\1}{$1\@povio/lightning-panda/playwright$1}g'

Replace e2e with the directories that hold your tests, fixtures and page objects. Run git diff afterwards and review it.

It leaves subpath imports such as @playwright/test/reporter alone. Custom reporters do not run under lightningpanda test, so remove those files or keep them out of the test directory.

Shared helpers count too

A helper module that still imports @playwright/test loads Playwright into the Bun test process. Search the whole repository, not only the test directory: grep -rn "@playwright/test\|from 'playwright'" --include='*.ts' .

3. The config file

lightningpanda test reads the first of these that exists:

1. The file named by -c / --config, or by $LP_CONFIG ($PLAYWRIGHT_CONFIG also works).
2. lightningpanda.config.ts, .mts, .mjs or .js in the working directory.
3. playwright.config.ts, .mts, .mjs or .js in the working directory.

So your existing playwright.config.ts works after its import is rewritten:

import { defineConfig, devices } from '@povio/lightning-panda/playwright';

export default defineConfig({
  testDir: './e2e',
  timeout: 30_000,
  retries: process.env.CI ? 2 : 0,
  use: { baseURL: 'http://localhost:3000' },
  projects: [{ name: 'chromium', use: { ...devices['Desktop Chrome'] } }],
  webServer: { command: 'bun run dev', url: 'http://localhost:3000', reuseExistingServer: !process.env.CI },
});

A lightningpanda.config.ts beside it takes precedence. That is how both runners can share one repository during a migration (see below).

Things to check in the config:

• Projects for other browsers. All projects run on Pyro, and lightningpanda test runs each file once, under the first project whose testDir / testMatch include it. A config with chromium, firefox and webkit projects therefore runs each test once, with the chromium project's use. Select one with --project.
• devices. Only five descriptors exist: Desktop Chrome, Desktop Chrome HiDPI, Desktop Edge, Pixel 7 and iPhone 15. Any other name is undefined, and spreading it adds nothing. Of a descriptor, viewport and userAgent take effect; deviceScaleFactor, isMobile and hasTouch do not.
• reporter is ignored. Pass --reporter list|line|dot on the command line.
• use.trace, use.video, use.screenshot are accepted and do nothing.

Config and the test runner lists every field that is honoured.

4. Run it

bunx lightningpanda test                 # all projects' files, half the CPUs as workers
bunx lightningpanda test e2e/checkout    # files whose path matches the regex
bunx lightningpanda test -g "closes" -j 4

You can also run a file with plain bun test, in one process, with $LP_CONFIG naming the config:

LP_CONFIG=playwright.config.ts bun test ./e2e/checkout.spec.ts

The difference: under plain bun test, Bun reports a test that calls test.skip() at run time as passed, because Bun cannot mark a running test as skipped. Workers, fullyParallel and the runner's own report also need lightningpanda test. Use plain bun test for quick runs of one file.

5. package.json scripts

{
  "scripts": {
    "e2e": "lightningpanda test",
    "e2e:update": "lightningpanda test -u",
    "e2e:one": "LP_CONFIG=playwright.config.ts bun test"
  }
}

Drop scripts that use playwright show-report, playwright codegen, --ui, --trace or --shard. They have no equivalent (see Overview).

6. Remove Playwright

Once nothing imports it:

bun remove @playwright/test playwright playwright-core
# or
npm uninstall @playwright/test playwright playwright-core

Also remove npx playwright install from setup scripts, Dockerfiles and CI, and any @playwright/test entry in tsconfig.json types.

7. CI

The browser comes with the npm package, so CI needs Node or Bun for the install, and Bun for the run. On GitHub Actions:

jobs:
  e2e:
    runs-on: ubuntu-24.04          # glibc 2.39
    steps:
      - uses: actions/checkout@v4
      - uses: oven-sh/setup-bun@v2
      - run: bun install --frozen-lockfile
      - run: bunx lightningpanda test --reporter dot

Compared with a Playwright job:

• Remove the npx playwright install --with-deps step and any browser cache.
• Remove --shard=i/n matrices; lightningpanda test has no sharding. Use more workers (-j) on one machine instead.
• Remove steps that upload playwright-report/ or traces. On failure, test-results/ (the outputDir) still holds -actual, -expected and -diff images of screenshot mismatches.
• The runner exits with status 1 when a test fails.

For more CI patterns see CI recipes.

8. Re-baseline screenshots

Pyro renders pages with its own CPU renderer. Screenshots differ from Chromium's at the pixel level, so every existing toHaveScreenshot baseline will fail. Write new ones once, review them, and commit them:

bunx lightningpanda test -u all

Commit the .json file written beside each .png: it holds the render's display-list hash, which lets later runs pass without rasterizing. See Screenshots and snapshots.

Running both side by side

You do not have to switch the whole suite at once. Two ways work.

Split the files between two configs. lightningpanda test prefers lightningpanda.config.ts; playwright test only reads playwright.config.ts. Give each runner its own files:

// lightningpanda.config.ts: the migrated files
import { defineConfig } from '@povio/lightning-panda/playwright';
export default defineConfig({
  testDir: './e2e',
  testMatch: ['checkout.spec.ts', 'positions/*.spec.ts'],
  use: { baseURL: 'http://localhost:3000' },
});

// playwright.config.ts: still on Playwright, skips the migrated files
import { defineConfig } from '@playwright/test';
export default defineConfig({
  testDir: './e2e',
  testIgnore: ['checkout.spec.ts', 'positions/*.spec.ts'],
  use: { baseURL: 'http://localhost:3000' },
});

Rewrite the imports of a file when you move it to the first list. Keep shared fixtures in two copies, or migrate them first.

Switch one fixtures module. If all tests import test and expect from a local module, that module can pick the implementation. The package's own parity suite works this way (packages/lightning-panda/test/playwright/fixtures.ts):

// e2e/fixtures.ts (an ES module project)
import * as lp from '@povio/lightning-panda/playwright';

const stock = process.env.PW_STOCK ? await import('@playwright/test') : undefined;
export const test: typeof lp.test = stock ? (stock.test as any) : lp.test;
export const expect: typeof lp.expect = stock ? (stock.expect as any) : lp.expect;

PW_STOCK=1 npx playwright test runs the suite on Playwright and Chromium; bunx lightningpanda test runs it on Pyro. Comparing the two runs shows which failures come from the migration.

Typical first failures

Symptom	Cause	Fix
page.click is not a function (also page.fill, page.textContent(selector), page.isVisible(selector), ...)	Playwright's selector-first page methods are not implemented.	Use locators: page.locator(selector).click().
Every toHaveScreenshot fails	Baselines came from Chromium.	Re-baseline with -u all (step 8).
unknown field 'animations' (or mask, caret, scale, omitBackground)	toHaveScreenshot accepts only threshold, maxDiffPixels, maxDiffPixelRatio, clip, fullPage and timeout.	Remove the option.
An assertion on a loading spinner or "Saving..." text times out	Actions settle before they return; the transient state is already gone.	Assert the final state, or wait for the request. See Behaviour differences.
A confirm() dialog acts as if Cancel was pressed	A dialog with no page.on('dialog') listener is dismissed.	Register a listener before the action, as Playwright requires.
toHaveRole('button') fails on a <button>	toHaveRole reads the role attribute only, not implicit roles.	Use getByRole('button') to find it, or drop the assertion.
An element inside an open shadow root is not found	CSS and getByRole locators do not enter shadow roots (measured on 0.0.33); getByText does.	Locate by text, or test through the host element's API.
Each test runs once although there are three browser projects	All projects run on Pyro, each file once.	Expected. Use --project to pick one.
await page.goto(url) returns null, or its response has no headers	Pooled pages turn goto into a route change, which returns null; a normal goto response carries status and URL only.	Check status with waitForResponse, or read headers from page.request.
afterEach that takes a screenshot when testInfo.status !== testInfo.expectedStatus never fires	testInfo.status stays 'passed' during hooks.	See Behaviour differences.
getByTestId(/regex/) or click({ clickCount: 3 }) throws "not supported yet"	Not implemented.	Use a string test id; use dblclick() or evaluate for triple clicks.
lightningpanda test: unknown option --shard	Flag not supported.	Remove it (see step 7).
App code reports an unsupported browser, or a web API is undefined	Pyro is not Chromium: its UA and API surface differ.	See Web platform support.

Checklist

• [ ] @povio/lightning-panda installed; bun --version works locally and in CI.
• [ ] No imports of @playwright/test, playwright, playwright/test or playwright-core left (grep -rn).
• [ ] Config file found (bunx lightningpanda test --list lists your tests).
• [ ] Browser-specific projects reviewed; devices names exist.
• [ ] Unsupported screenshot options removed; baselines rewritten with -u all and committed with their .json files.
• [ ] page.click(selector)-style calls rewritten as locators.
• [ ] Dialog listeners registered where the app uses confirm, alert or prompt.
• [ ] Assertions on transient states rewritten.
• [ ] package.json scripts and CI updated; playwright install, report uploads and sharding removed.
• [ ] Playwright packages removed.
• [ ] Optional: slow app boots moved to booted pages.