During the hang, ps shows a stuck adb child of the dartvm process sitting at 0% CPU. Either force-stop or uninstall can be the stuck command — both hang on CPU-starved emulators:

# Run 1 — force-stop hung:
runner  87946 dartvm  0.0  0.0  05:30  adb -s emulator-5554 shell am force-stop com.example.app

# Run 2 — uninstall hung (force-stop was killed by watchdog, uninstall also stuck):
runner  62121 dartvm  0.0  0.0  12:00  adb -s emulator-5554 uninstall com.example.app

Killing the stuck adb process unblocks everything:

$ kill -9 87946
$ kill -9 88799    # uninstall also stuck, kill it too
adb uninstall failed: ProcessException: exit code -9   # this error is normal
🎉 49 tests passed.
# flutter test exits with code 0

Consistent across 6+ runs. Killing the stuck adb children fixed it every time.

Where it hangs:

kill() in integration_test_device.dart runs two adb commands sequentially. Both have no timeout and both can hang:

finalize()
  testDevice.kill()
    device.stopApp(package)        <-- adb shell am force-stop (no timeout)
    device.uninstallApp(package)   <-- adb uninstall (no timeout)
    device.dispose()
    _ddsLauncher.shutdown()

• stopApp() in android_device.dart calls _processUtils.stream() — no timeout parameter
• uninstallApp() in android_device.dart calls _processUtils.run() — no timeout parameter

Why am force-stop and uninstall hang:

On macos-15-intel the emulator's qemu uses ~200% CPU for SwiftShader rendering (4-core host).

am force-stop calls ActivityManagerService.forceStopPackage() in system_server via Binder IPC (AOSP source). uninstall goes through PackageManagerService via the same Binder mechanism. When system_server is CPU-starved, Binder calls to it hang.

getprop reads from kernel shared memory via __system_property_read_callback() with no IPC (AOSP source). Works fine regardless of CPU pressure.

During the hang:

• adb devices works (host-side adb server, never enters emulator)
• adb shell getprop sys.boot_completed returns 1 (kernel shared memory read)
• adb shell am force-stop hangs (Binder IPC to starved system_server)
• adb uninstall hangs (Binder IPC to starved system_server)

Source locations in Flutter:

• stopApp(): android_device.dart — calls _processUtils.stream() with no timeout
• uninstallApp(): android_device.dart — calls _processUtils.run() with no timeout
• kill(): integration_test_device.dart — awaits both sequentially, no timeout
• finalize(): flutter_platform.dart — no timeout on finalizers

Possible fixes:

• Add a timeout to stopApp() and uninstallApp() that kills the adb process after a few seconds and returns false
• Add a timeout parameter to _processUtils.stream() and _processUtils.run()
• Use adb shell kill instead of am force-stop since the kernel syscall works even when system_server is starved

Our workaround:

Background watchdog that searches for the two specific adb commands Flutter runs in teardown (force-stop and uninstall) and kills them:

flutter test integration_test/app_test.dart &
CMD_PID=$!

(
  while kill -0 $CMD_PID 2>/dev/null; do
    sleep 30
    for pattern in force-stop uninstall; do
      for pid in $(pgrep -f "$pattern"); do
        PCMD=$(ps -p "$pid" -o args=)
        echo "$PCMD" | grep -q adb || continue
        echo "Killing stuck adb $pattern (PID $pid)"
        kill -9 "$pid"
      done
    done
  done
) &

wait $CMD_PID