#vulnerable code 
                                @Test
    public void testConflictingConnections() {
        try (TestLog log = new TestLog(OperationMapper.class)) {
            new TestSchemaGenerator()
                    .withOperationsFromSingleton(new ConflictingBookService())
                    .generate();
            assertEquals(1, log.getEvents().size());
            ILoggingEvent event = log.getEvents().get(0);
            assertThat(event.getLevel(), is(Level.WARN));
            assertThat(event.getMessage(), containsString(Urls.Errors.NON_UNIQUE_TYPE_NAME));
        }
    } 
                            #location 7 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testConflictingConnections() {
        try (TestLog log = new TestLog(OperationMapper.class)) {
            new TestSchemaGenerator()
                    .withOperationsFromSingleton(new ConflictingBookService())
                    .generate();
            assertWarningsLogged(log.getEvents(), Urls.Errors.NON_UNIQUE_TYPE_NAME);
        }
    }