public void prepareExchange(Exchange exchange) {
        Message message = exchange.getMessage();
        String recipients = matchFilters(exchange);
        message.setHeader(RECIPIENT_LIST_HEADER, recipients);
    }
@Test
    void testPrepareExchange() {
        when(exchange.getMessage()).thenReturn(message);
        when(filterService.getMatchingEndpointsForExchangeByChannel(exchange, TEST_CHANNEL, true, false))
                .thenReturn(MOCK_ENDPOINT);
        processor.prepareExchange(exchange);
        verify(message, new Times(1)).setHeader(RECIPIENT_LIST_HEADER, MOCK_ENDPOINT);
    }