skills/playwright/SKILL.md

---
name: playwright
description: Add and run Playwright E2E tests for any project with a web UI — covers setup, HTMX-specific patterns, SSE/streaming, Taskfile integration, and CI wiring.
---

# Playwright E2E Testing

## When to use

- Project has a web UI (HTMX, React, plain HTML — any stack)
- You want to verify the golden path in a real browser, not just unit-test handlers
- Chat/SSE streams, HTMX swaps, or dynamic DOM need testing that Go tests cannot cover

## Setup (first time in a project)

### 1. Install

```bash
npm init -y
npm install --save-dev @playwright/test
npx playwright install chromium   # chromium only — enough for CI
```

### 2. Directory layout

```
<repo>/
  e2e/
    playwright.config.ts
    tests/
      smoke.spec.ts
      chat.spec.ts
  package.json
  Taskfile.yml          ← add e2e task here
```

Keep `e2e/` at repo root. Add to `.gitignore`:
```
node_modules/
e2e/test-results/
e2e/playwright-report/
```

### 3. Config (`e2e/playwright.config.ts`)

```typescript
import { defineConfig, devices } from '@playwright/test';

export default defineConfig({
  testDir: './tests',
  timeout: 30_000,
  retries: process.env.CI ? 2 : 0,
  reporter: process.env.CI ? 'github' : 'list',
  use: {
    baseURL: process.env.BASE_URL ?? 'http://localhost:8080',
    screenshot: 'only-on-failure',
    trace: 'retain-on-failure',
  },
  projects: [
    { name: 'chromium', use: { ...devices['Desktop Chrome'] } },
  ],
});
```

### 4. Taskfile task

```yaml
tasks:
  e2e:
    desc: "Run Playwright E2E tests against running dev server"
    dir: e2e
    cmds:
      - npx playwright test {{.CLI_ARGS}}
    env:
      BASE_URL: "http://localhost:8080"

  e2e:ui:
    desc: "Open Playwright UI mode"
    dir: e2e
    cmds:
      - npx playwright test --ui
```

Run with: `task e2e` or `task e2e -- --headed` or `task e2e -- tests/chat.spec.ts`

---

## HTMX-specific patterns

HTMX updates the DOM asynchronously. Never use `waitForSelector` alone — wait for HTMX to finish the swap.

### Wait for HTMX swap to complete

```typescript
// After triggering an action that causes an HTMX request:
await page.locator('[hx-target]').waitFor({ state: 'visible' });

// Better: wait for htmx:afterSwap event on the target element
await page.evaluate(() =>
  new Promise<void>(resolve =>
    document.body.addEventListener('htmx:afterSwap', () => resolve(), { once: true })
  )
);
```

### Wait for specific content to appear after swap

```typescript
await page.locator('#result').waitFor({ state: 'visible' });
await expect(page.locator('#result')).toContainText('expected text');
```

### Avoid timing races

```typescript
// BAD — may grab stale content before swap completes
await page.click('button');
const text = await page.locator('#output').textContent();

// GOOD — assert after waiting
await page.click('button');
await expect(page.locator('#output')).toContainText('expected text', { timeout: 5000 });
```

### Forms with HTMX submit

```typescript
await page.fill('input[name="query"]', 'hello');
await page.keyboard.press('Enter');           // or click submit button
await expect(page.locator('#response')).not.toBeEmpty({ timeout: 10_000 });
```

---

## SSE / streaming patterns

For chat UIs or any endpoint using `text/event-stream`:

```typescript
test('chat stream delivers response', async ({ page }) => {
  await page.goto('/chat');

  // Type and submit
  await page.fill('#message-input', 'what is 2+2?');
  await page.click('#send-btn');

  // SSE response appears incrementally — wait for streaming to stop
  // Strategy: wait until the response element stops growing
  const responseEl = page.locator('#chat-response');
  await responseEl.waitFor({ state: 'visible', timeout: 15_000 });

  // Poll until content stabilises (streaming done)
  let prev = '';
  let stable = 0;
  while (stable < 3) {
    const cur = await responseEl.textContent() ?? '';
    if (cur === prev && cur.length > 0) stable++;
    else { stable = 0; prev = cur; }
    await page.waitForTimeout(300);
  }

  expect(prev.length).toBeGreaterThan(0);
});
```

For a done-signal in the DOM (e.g. a `[data-streaming="false"]` attribute set when stream ends):

```typescript
await page.locator('[data-streaming="false"]').waitFor({ timeout: 20_000 });
const text = await page.locator('#chat-response').textContent();
expect(text).toBeTruthy();
```

---

## Golden path smoke test template

```typescript
// e2e/tests/smoke.spec.ts
import { test, expect } from '@playwright/test';

test.describe('smoke', () => {
  test('home page loads', async ({ page }) => {
    await page.goto('/');
    await expect(page).toHaveTitle(/.+/);
    await expect(page.locator('body')).not.toBeEmpty();
  });

  test('main nav is present', async ({ page }) => {
    await page.goto('/');
    await expect(page.locator('nav')).toBeVisible();
  });
});
```

---

## Screenshot on failure

Already configured via `screenshot: 'only-on-failure'` in the config. Artifacts land in `e2e/test-results/`. View them with:

```bash
npx playwright show-report e2e/playwright-report
```

---

## CI wiring (Gitea workflow)

```yaml
  e2e:
    runs-on: ubuntu-latest
    needs: build
    steps:
      - uses: actions/checkout@v4

      - name: Install Node deps
        working-directory: e2e
        run: npm ci

      - name: Install Playwright browsers
        working-directory: e2e
        run: npx playwright install --with-deps chromium

      - name: Start server
        run: ./bin/server &
        env:
          PORT: 8080

      - name: Wait for server
        run: |
          for i in $(seq 1 20); do
            curl -sf http://localhost:8080/ && break
            sleep 1
          done

      - name: Run E2E tests
        working-directory: e2e
        run: npx playwright test
        env:
          BASE_URL: http://localhost:8080

      - name: Upload test artifacts
        if: failure()
        uses: actions/upload-artifact@v4
        with:
          name: playwright-report
          path: e2e/playwright-report/
```

---

## Checklist

When adding Playwright to a project:

- [ ] `npm init -y && npm install --save-dev @playwright/test` in `e2e/`
- [ ] `npx playwright install chromium`
- [ ] `e2e/playwright.config.ts` with baseURL and screenshot on failure
- [ ] At least one smoke test covering the golden path
- [ ] `.gitignore` entries: `node_modules/`, `test-results/`, `playwright-report/`
- [ ] `task e2e` wired in Taskfile.yml
- [ ] CI step added to Gitea workflow

## Failure triage

| Symptom | Likely cause | Fix |
|---------|-------------|-----|
| `TimeoutError` on HTMX element | Swap not finished | Use `htmx:afterSwap` event or increase timeout |
| Stale content asserted | Race between click and swap | Move assertion after explicit wait |
| SSE test flaky | Stream not done yet | Poll for stable content or use done-signal attribute |
| CI fails, local passes | Server not ready | Add wait-for-server loop in CI |
| Screenshots empty | Screenshot taken before render | Add `await page.waitForLoadState('networkidle')` |