Mobile Firefox (Android emulator) verification — 2026-07-11¶

Goal¶

Per the sequencing directive ("finish desktop first, then the lightest emulator for mobile Firefox"), verify the extension's core behavior on real Firefox for Android, fully headless and automated, on an 8 GB M1. Logged-out only.

Environment (lightest workable path)¶

• Toolchain: Homebrew openjdk (26) + android-commandlinetools; sdkmanager installs platform-tools, emulator, and the system-images;android-34;aosp_atd;arm64-v8a image (AOSP Automated-Test-Device — the lightest arm64 image: stripped UI, fast boot, low RAM; native on Apple Silicon, no x86 translation).
• AVD: yta_test, booted headless: -no-window -no-audio -no-boot-anim -gpu swiftshader_indirect -memory 1536. Booted in seconds; host stayed ~21-27% RAM free throughout (workable on 8 GB).
• Browser: Firefox Nightly (Fenix 154.0a1, org.mozilla.fenix), official arm64-v8a APK from archive.mozilla.org/pub/fenix/nightly/..., sideloaded with adb install.

Headless techniques that made it work (not in doc 18, worth keeping)¶

• screencap returns a blank surface under headless swiftshader → drive the UI by the accessibility tree instead: adb shell uiautomator dump gives every node's text + bounds, so taps are computed from the XML with no pixels. Helper: tests/e2e/android/ui.py. Used to walk Fenix onboarding and toggle Settings → Advanced → Remote debugging via USB (confirmed by the @org.mozilla.fenix/firefox-debugger-socket unix socket appearing in /proc/net/unix).
• adb root (the aosp_atd image is userdebug) is required for geckodriver to push its profile: without it the session dies with adb error: fchown failed: Operation not permitted (Fenix Nightly is not debuggable, so geckodriver's app-storage run-as path fails; root lets it chown the pushed profile).
• geckodriver + Marionette (not web-ext) drives Fenix, so the same executeScript DOM-marker assertions as the desktop bench apply. selenium enableMobile('org.mozilla.fenix') with no serial (geckodriver auto-detects the single device; selenium's deviceSerial field is rejected by geckodriver 0.37). Extension loaded via driver.installAddon(xpi, /*temporary*/ true) — no signing. Defaults already have audioOnlyEnabled:true, so no settings seeding is needed.

Result — tests/e2e/probe-mobile-fenix.mjs, 4/4 PASS¶

Extension installs as a temporary add-on (youtube-audio@local); content script injects on m.youtube.com (data-yta-bench=1).

Conclusions: the MV2 build loads and runs on Firefox for Android; the credentialless ANDROID_VR fetch + <video>.src hijack works on the mobile (m.youtube.com) DOM; and both fallback branches (kids-UNPLAYABLE and the newly-fixed live exclusion) behave correctly on mobile, exactly as on desktop.

Reproduce¶

export JAVA_HOME=/opt/homebrew/opt/openjdk
export ANDROID_SDK_ROOT=/opt/homebrew/share/android-commandlinetools
export PATH="$ANDROID_SDK_ROOT/platform-tools:$ANDROID_SDK_ROOT/emulator:$PATH"
emulator @yta_test -no-window -no-audio -no-boot-anim -gpu swiftshader_indirect -memory 1536 &
adb wait-for-device && adb root
# (first time only) sideload Fenix + enable Remote debugging via tests/e2e/android/ui.py
node tests/e2e/probe-mobile-fenix.mjs dist/youtube-audio-bench.xpi

Not covered on mobile (honest carve-out)¶

Background/lock-screen mediaSession controls and the popup/options UI rendering are not asserted here (headless, no compositor). Core playback + protection logic is identical JS to desktop (same Gecko), and is proven on both surfaces.