Add checks for widget/window leaks to kernel tests.

Change-Id: I52af87279e37e49ce2206c5c823fe8fb4caef338
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>

tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp

@@ -64,6 +64,7 @@ class tst_QGuiApplication: public tst_QCoreApplication
     Q_OBJECT
 
 private slots:
+    void cleanup();
     void displayName();
     void firstWindowTitle();
     void windowIcon();
@@ -80,6 +81,11 @@ private slots:
     void layoutDirection();
 };
 
+void tst_QGuiApplication::cleanup()
+{
+    QVERIFY(QGuiApplication::allWindows().isEmpty());
+}
+
 void tst_QGuiApplication::displayName()
 {
     int argc = 1;

tests/auto/gui/kernel/qwindow/tst_qwindow.cpp

@@ -101,11 +101,17 @@ private slots:
         touchDevice->setType(QTouchDevice::TouchScreen);
         QWindowSystemInterface::registerTouchDevice(touchDevice);
     }
+    void cleanup();
 
 private:
     QTouchDevice *touchDevice;
 };
 
+void tst_QWindow::cleanup()
+{
+    QVERIFY(QGuiApplication::allWindows().isEmpty());
+}
+
 void tst_QWindow::mapGlobal()
 {
     QWindow a;

tests/auto/widgets/kernel/qapplication/tst_qapplication.cpp

@@ -260,6 +260,7 @@ void tst_QApplication::cleanup()
 {
 // TODO: Add cleanup code here.
 // This will be executed immediately after each test is run.
+    QVERIFY(QApplication::topLevelWidgets().isEmpty());
 }
 
 void tst_QApplication::staticSetup()

tests/auto/widgets/kernel/qwidget_window/tst_qwidget_window.cpp

@@ -61,7 +61,7 @@ static inline void setFrameless(QWidget *w)
     w->setWindowFlags(flags);
 }
 
-class tst_QWidget_window : public QWidget
+class tst_QWidget_window : public QObject
 {
     Q_OBJECT
 
@@ -71,6 +71,7 @@ public:
 public slots:
     void initTestCase();
     void cleanupTestCase();
+    void cleanup();
 
 private slots:
     void tst_min_max_size();
@@ -106,6 +107,11 @@ void tst_QWidget_window::cleanupTestCase()
 {
 }
 
+void tst_QWidget_window::cleanup()
+{
+    QVERIFY(QApplication::topLevelWidgets().isEmpty());
+}
+
 /* Test if the maximum/minimum size constraints
  * are propagated from the widget to the QWidgetWindow
  * independently of whether they were set before or after