Authors Linux desktop UI tests via AT-SPI - the DBus-based Assistive Technology Service Provider Interface implemented by `at-spi2-core` (registry daemon + `libatspi` C library + ATK GTK bridge). Covers enabling toolkit accessibility (`gsettings set org.gnome.desktop.interface toolkit-accessibility true`), driving GTK + Qt apps through Python `dogtail` (object-oriented + procedural APIs), inspecting the tree with Accerciser, scripting via `pyatspi`, and CI integration on headless Linux runners with `Xvfb` + `dbus-launch`. Use for Linux-side desktop tests of GTK applications, Qt apps with QAccessible enabled, and Electron apps on Linux.