#include <QApplication>
#include <QTest>
#include "test_engine.hpp"

int main( int argc, char *argv[] ) {
    QApplication a( argc, argv );
    QTest::qExec( new Test_Engine, argc, argv );

    return a.exec();
}

#include <QCoreApplication>
#include <QTest>
#include "test_engine.hpp"

int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);
    QTest::qExec( new Test_Engine, argc, argv );

    return a.exec();
}

--- 
+++ 
@@ -1,9 +1,9 @@
-#include <QCoreApplication>
+#include <QApplication>
 #include <QTest>
 #include "test_engine.hpp"
 
-int main(int argc, char *argv[]) {
-    QCoreApplication a(argc, argv);
+int main( int argc, char *argv[] ) {
+    QApplication a( argc, argv );
     QTest::qExec( new Test_Engine, argc, argv );
 
     return a.exec();
Replace QCoreApplication to QAppliation for QWidget work.
