#vulnerable code 
                                @Test
    public void testDownstreamDisconnectTriggersReconnect(final TestContext ctx) {

        final ProtonConnection connectionToCreate = mock(ProtonConnection.class);
        when(connectionToCreate.getRemoteContainer()).thenReturn("server");
        // expect the connection factory to be invoked twice
        // first on initial connection
        // second on re-connect attempt
        DisconnectHandlerProvidingConnectionFactory connectionFactory = new DisconnectHandlerProvidingConnectionFactory(connectionToCreate, 2);

        // GIVEN an client connected to a server
        final Async connected = ctx.async();
        HonoClientImpl client = new HonoClientImpl(vertx, connectionFactory);
        client.connect(new ProtonClientOptions().setReconnectAttempts(1), ctx.asyncAssertSuccess(ok -> connected.complete()));
        connected.await(200);

        // WHEN the downstream connection fails
        connectionFactory.getDisconnectHandler().handle(connectionToCreate);

        // THEN the adapter tries to reconnect to the downstream container
        connectionFactory.await(1, TimeUnit.SECONDS);
    } 
                            #location 18 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testDownstreamDisconnectTriggersReconnect(final TestContext ctx) {

        // expect the connection factory to be invoked twice
        // first on initial connection
        // second on re-connect attempt
        connectionFactory = new DisconnectHandlerProvidingConnectionFactory(con, 2);

        // GIVEN an client connected to a server
        final Async connected = ctx.async();
        final HonoClientImpl client = new HonoClientImpl(vertx, connectionFactory);
        client.connect(new ProtonClientOptions().setReconnectAttempts(1), ctx.asyncAssertSuccess(ok -> connected.complete()));
        connected.await();

        // WHEN the downstream connection fails
        connectionFactory.getDisconnectHandler().handle(con);

        // THEN the adapter reconnects to the downstream container
        connectionFactory.await(1, TimeUnit.SECONDS);
    }