#fixed code
                                @Override
    protected Object createTest() throws Exception {
        instances = createHierarchicalFixtures();
        return instances.getLast();
    }
#vulnerable code 
                                @Override
    protected Object createTest() throws Exception {
        ensureHierarchicalFixturesAreValid();
        return instances.getLast();
    } 
                            #location 4 
                            #vulnerability type THREAD_SAFETY_VIOLATION