Authors and runs Qt Test - the first-party C++ unit + GUI test framework that ships with Qt 6 (via the `QtTest` module header). Covers the `QTEST_MAIN` / `QTEST_APPLESS_MAIN` / `QTEST_GUILESS_MAIN` entry-point macros, the `QObject` private-slot test pattern, `QVERIFY` / `QCOMPARE` / `QFETCH` assertions, GUI event simulation (`QTest::mouseClick`, `QTest::keyClick`, `QTest::touchEvent`), `QSignalSpy` for signal introspection, `QBENCHMARK` for performance regression, and the `-o file,junitxml` CI output. Use for in-process testing of Qt widgets, QObject signal/slot chains, and Qt Quick / QML application logic; for out-of-process Qt-app driving, use an OS-native accessibility driver instead.