Test results window lists test cases of new added test class twice

I'm using auto-test in following manner:

Define maintest.cpp with main function:

// includes...

int main(int argc, char *argv[]) {
    QCoreApplication app(argc, argv);
    app.exit(0);

    int status = 0;

    TestClass1 tC1;
    status |= QTest::qExec(&tC1, argc, argv);

    TestClass2 tC2;
    status |= QTest::qExec(&tC2, argc, argv);

    return status;
}

In the test classes are the test cases defined as private slots.

Generally, this approach works fine.

But:

If I'm adding a new test class (TestClass 3 for example) and run tests, the results of the last added test class will be listed twice in test results window (see screenshot in attachment). Also the number of failed tests from the last test class is counted twofold.

The bug can be obviated by restarting QT-Creator. The test class will be listed once then.