    @Test
    public void testSingleElement() throws IOException {

        DataPacketDto dataPacketDto = new DataPacketDto("test-data".getBytes(StandardCharsets.UTF_8)).putAttribute("key", "value");
        objectMapper.writeValue(data, Arrays.stream(new DataPacketDto[]{dataPacketDto}).collect(Collectors.toList()));
        assertEquals(transactionCompletion, senderSupplier.get().sendFiles());
        verify(transaction).send(dataPacketDto.toDataPacket());
        verify(transaction).complete();
        verifyNoMoreInteractions(siteToSiteClient, transaction, transactionCompletion);
    }