qtquick: Fix resizing root view

And uncommented the qtquick test for this, which now passes.
Moved the test to its own qtquick tests file.

tests/qtquick/tst_qtquick.cpp

@@ -0,0 +1,95 @@
+/*
+  This file is part of KDDockWidgets.
+
+  SPDX-FileCopyrightText: 2019-2022 Klarälvdalens Datakonsult AB, a KDAB Group company <info@kdab.com>
+  Author: Sérgio Martins <sergio.martins@kdab.com>
+
+  SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only
+
+  Contact KDAB at <info@kdab.com> for commercial licensing options.
+*/
+
+/// @file
+/// @brief Here lives the tests that only apply to QtQuick
+
+#include "Platform.h"
+#include "KDDockWidgets.h"
+
+#include "../utils.h"
+
+#include <QtTest/QtTest>
+#include <QQmlApplicationEngine>
+
+using namespace KDDockWidgets;
+using namespace KDDockWidgets::Tests;
+using namespace KDDockWidgets::Controllers;
+
+class TestQtQuick : public QObject
+{
+    Q_OBJECT
+
+public Q_SLOTS:
+    void initTestCase();
+    void cleanupTestCase();
+
+private Q_SLOTS:
+    void tst_restoreRestoresMainWindowPosition();
+};
+
+
+void TestQtQuick::initTestCase()
+{
+    KDDockWidgets::Platform::instance()->installMessageHandler();
+}
+
+void TestQtQuick::cleanupTestCase()
+{
+    KDDockWidgets::Platform::instance()->uninstallMessageHandler();
+}
+
+void TestQtQuick::tst_restoreRestoresMainWindowPosition()
+{
+    // Tests the ApplicationWindow {} case
+
+    QQmlApplicationEngine engine(":/main2.qml");
+
+    const auto mainWindows = DockRegistry::self()->mainwindows();
+    QCOMPARE(mainWindows.size(), 1);
+    MainWindow *mainWindow = mainWindows.first();
+    QVERIFY(mainWindow->isVisible());
+
+    QCOMPARE(mainWindow->pos(), QPoint(0, 0));
+
+    Window::Ptr window = mainWindow->view()->window();
+
+    LayoutSaver saver;
+    const QByteArray saved = saver.serializeLayout();
+
+    const QPoint originalPos = window->framePosition();
+
+    const QPoint newPos = originalPos + QPoint(200, 200);
+    window->setFramePosition(newPos);
+    QCOMPARE(window->framePosition(), newPos);
+
+    QVERIFY(saver.restoreLayout(saved));
+
+    QCOMPARE(window->framePosition(), originalPos);
+
+    delete mainWindow;
+}
+
+int main(int argc, char *argv[])
+{
+    KDDockWidgets::Platform::tests_initPlatform(argc, argv, KDDockWidgets::FrontendType::QtQuick);
+
+    if (shouldSkipTests())
+        return 0;
+
+    TestQtQuick test;
+    const int exitCode = QTest::qExec(&test, argc, argv);
+    KDDockWidgets::Platform::tests_deinitPlatform();
+
+    return exitCode;
+}
+
+#include "tst_qtquick.moc"