| name | test-perf |
| description | Run performance and Core Web Vitals testing on a URL. Use when user wants to test page speed, LCP, CLS, INP, load times, asset optimization, or runtime performance. |
| allowed-tools | Bash(playwright-cli:*) Bash(npx:*) Bash(mkdir:*) |
Performance & Core Web Vitals
Run 25 performance test cases across 3 parallel agents covering page load/CWV, runtime performance, and asset optimization.
Setup
URL="${ARGUMENTS:-http://localhost:3000}"
TIMESTAMP=$(date +%Y%m%d-%H%M%S)
OUTDIR="test-results/test-perf/$TIMESTAMP"
mkdir -p "$OUTDIR/screenshots" "$OUTDIR/snapshots" "$OUTDIR/traces"
Parallel Execution — 3 Subagents
Agent 1: Loading (-s=perf-loading)
Tests page load performance and Core Web Vitals.
playwright-cli -s=perf-loading open "$URL"
playwright-cli -s=perf-loading tracing-start
Test Cases:
| TC | Test | How to Check |
|---|
| TC-P1 | Time to first meaningful paint | run-code to read performance.getEntriesByType('paint') for first-contentful-paint timing |
| TC-P2 | LCP ≤2.5s | run-code with PerformanceObserver for largest-contentful-paint entry, check startTime ≤ 2500 |
| TC-P3 | FID/INP ≤200ms | run-code with PerformanceObserver for first-input and event entries, check delay ≤ 200ms |
| TC-P4 | CLS ≤0.1 | run-code with PerformanceObserver for layout-shift entries (no hadRecentInput), sum values, check ≤ 0.1 |
| TC-P5 | Time to Interactive (TTI) | run-code to measure time until main thread is idle: performance.timing.domInteractive - performance.timing.navigationStart |
| TC-P6 | Total page weight <3MB | run-code to sum performance.getEntriesByType('resource').map(r => r.transferSize), check < 3MB |
| TC-P7 | DOM node count <1500 | run-code: document.querySelectorAll('*').length, flag if >1500 |
| TC-P8 | Render-blocking resources count | run-code to find <link rel="stylesheet"> in <head> without media attr and <script> without defer/async |
playwright-cli -s=perf-loading tracing-stop
playwright-cli -s=perf-loading close
Agent 2: Runtime (-s=perf-runtime)
Tests runtime performance and interaction responsiveness.
playwright-cli -s=perf-runtime open "$URL"
playwright-cli -s=perf-runtime tracing-start
Test Cases:
| TC | Test | How to Check |
|---|
| TC-P9 | Long tasks (>50ms) detected | run-code with PerformanceObserver for longtask entries, report count and durations |
| TC-P10 | Memory usage / leaks | run-code: performance.memory (Chrome only) — check usedJSHeapSize, compare before/after interactions |
| TC-P11 | Scroll performance (no jank) | run-code to scroll page while measuring frame timing via requestAnimationFrame, flag >16ms gaps |
| TC-P12 | Animation frame rate | run-code to measure 60 frames via requestAnimationFrame, calculate avg fps, flag <30fps |
| TC-P13 | Input responsiveness | run-code to measure time from click event to next paint via PerformanceObserver event entries |
| TC-P14 | Lazy loading works | run-code to check images below fold have loading="lazy" and aren't loaded until scroll |
| TC-P15 | Skeleton/loading states appear before content | run-code to intercept network requests, verify skeleton UI renders while data loads |
playwright-cli -s=perf-runtime tracing-stop
playwright-cli -s=perf-runtime close
Agent 3: Assets (-s=perf-assets)
Tests asset optimization and network efficiency.
playwright-cli -s=perf-assets open "$URL"
playwright-cli -s=perf-assets tracing-start
Test Cases:
| TC | Test | How to Check |
|---|
| TC-P16 | Images use modern formats (WebP/AVIF) | run-code to check image src extensions and Content-Type from performance entries |
| TC-P17 | Images have explicit width/height | run-code to find <img> elements without width and height attributes (causes CLS) |
| TC-P18 | Images lazy loaded | run-code to find below-fold images, check for loading="lazy" attribute |
| TC-P19 | CSS/JS minified | run-code to fetch CSS/JS resources, check file size and whitespace ratio |
| TC-P20 | Gzip/Brotli compression enabled | run-code to check Content-Encoding header on resources via performance entries |
| TC-P21 | Browser caching headers | run-code to fetch resources and check Cache-Control, ETag, Expires headers |
| TC-P22 | No unused CSS/JS (coverage) | run-code with page.coverage.startCSSCoverage() / startJSCoverage(), report unused percentage |
| TC-P23 | Font loading strategy | run-code to check @font-face rules for font-display: swap or optional |
| TC-P24 | Preconnect/prefetch hints | run-code to find <link rel="preconnect/prefetch/preload"> for third-party origins |
| TC-P25 | HTTP/2 or HTTP/3 used | run-code to check nextHopProtocol from performance.getEntriesByType('resource') |
playwright-cli -s=perf-assets tracing-stop
playwright-cli -s=perf-assets close
Report Generation
After all 3 agents complete, merge results into $OUTDIR/report.md.
Include a performance scorecard:
| Metric | Value | Target | Status |
|---|
| LCP | Xs | ≤2.5s | ✅/❌ |
| CLS | X | ≤0.1 | ✅/❌ |
| INP | Xms | ≤200ms | ✅/❌ |
| Page Weight | XMB | <3MB | ✅/❌ |
| DOM Nodes | X | <1500 | ✅/❌ |
Group detailed results:
- Loading (TC-P1 through TC-P8)
- Runtime (TC-P9 through TC-P15)
- Assets (TC-P16 through TC-P25)
Cleanup
playwright-cli -s=perf-loading close 2>/dev/null
playwright-cli -s=perf-runtime close 2>/dev/null
playwright-cli -s=perf-assets close 2>/dev/null
