Browser tests

End to end tests for the fullscreen photo viewer (scripts/lightbox.js and css/lightbox.css), driving a real headless Chromium with Playwright.

Running them

./tests/run.sh

First run creates tests/.venv and downloads Chromium (about 95 MB, cached in ~/Library/Caches/ms-playwright). After that it is just pytest. The whole suite takes about 20 seconds.

run.sh starts a Jekyll server if nothing is answering on http://localhost:4000, and builds the site once with the production config for the tests that check absolute URLs. Both happen there rather than in a fixture so that the parallel workers share them instead of racing to create their own.

./tests/run.sh -k swipe                  # only the swipe tests
./tests/run.sh -p no:xdist               # serially, for readable output
./tests/run.sh --durations=10            # find the slow ones
./tests/run.sh --headed --slowmo 400     # watch it happen in a window
./tests/run.sh --base-url http://localhost:4001

Tests run across all cores by default (-n auto). Distribution is per test, not per file: grouping by file pinned the largest module to one worker and left the rest idle, which cost about 50 seconds.

Layout

file
`conftest.py`	server startup, browser launch, `desktop` and `phone` fixtures
`viewer.py`	driver for the viewer: waits, gestures, state readers
`test_photo_viewer.py`	viewer behaviour
`test_gallery_links.py`	every photo URL resolves; no browser needed

desktop is a 1440x900 window with a mouse and keyboard. phone is an iPhone 13 with touch input and a coarse pointer, which matters because the prev/next arrows are hidden behind @media (hover: none) and (pointer: coarse).

Any console error or uncaught exception in the page fails the test that caused it, via an autouse fixture.

Notes

Photo counts are read from the page instead of being hardcoded, so adding posts will not break anything. Tests naming a specific album skip themselves if that post is gone.

Two kinds of input need raw CDP rather than Playwright’s own API:

Touch gestures are a sequence of Input.dispatchTouchEvent calls, since a swipe is many move events and Playwright only exposes taps.
A trackpad pinch on macOS is not a touch gesture at all. Chrome reports it as a wheel event with ctrlKey set, so it is sent as Input.dispatchMouseEvent with the Ctrl modifier. Without handling it the browser zooms the entire page.

Viewer.settle() waits for the photo to decode and for both the overlay and image fades to finish. Asserting or screenshotting before that catches the viewer mid-transition and looks like a transparency bug.