Playwright Screen Recording for Test Verification

Use Playwright's video recording to capture headless browser operations as .webm videos for PR review or bug fix verification.

Core Usage

from playwright.sync_api import sync_playwright
import tempfile
from pathlib import Path

video_dir = Path(tempfile.mkdtemp())

with sync_playwright() as pw:
    browser = pw.chromium.launch(headless=True)
    context = browser.new_context(
        viewport={"width": 1400, "height": 900},
        record_video_dir=str(video_dir),
        record_video_size={"width": 1400, "height": 900},
    )
    page = context.new_page()
    page.goto(f"file:///path/to/test.html")

    # ... perform test actions, add pauses for readability ...
    page.wait_for_timeout(800)  # pause so viewers can see the current state

    page.close()
    context.close()  # video is finalized after context.close()
    browser.close()

# Retrieve the recorded video
videos = list(video_dir.glob("*.webm"))
if videos:
    videos[0].rename("demo.webm")

Use Cases

• Bug fix verification: record before/after comparisons showing button state changes, UI behavior differences
• PR Review: attach .webm video so reviewers can visually understand the change
• Regression test evidence: record critical interaction paths as visual proof of passing tests

Recording Tips

Add pauses between actions

page.click(".some-button")
page.wait_for_timeout(800)  # let viewers see the click effect

page.keyboard.press("ArrowRight")
page.wait_for_timeout(600)  # let viewers see the navigation result

Combine assertions with terminal logging

state = get_nav_state(page)
print(f"[1] Title: {state['title']}")
print(f"    prev disabled: {state['prevDisabled']}  (expected: True)")
assert state["prevDisabled"] is True
print("    PASS")

Terminal output paired with the recorded video provides dual verification.

Prefer real data

Use existing real trace data from the project rather than synthetic data for more convincing demos:

# Build test HTML from a real trace file
records = []
with open(".traces/trace_xxx.jsonl") as f:
    for line in f:
        # Escape </script> to prevent breaking the HTML script block
        records.append(line.strip().replace("</script>", '</scr" + "ipt>'))

Notes

• Video format is .webm (VP8 codec), supported by most players and browsers
• Each page produces a separate video file
• record_video_size controls video resolution — keep it consistent with viewport
• Recording works in headless mode, no display required
• Video files are typically a few hundred KB, suitable for attaching to PRs or chat