    @Test
    public void testProcess() throws Exception {

        PoiExcelWriter poiExcelWriter = new PoiExcelWriter(20);
        final Resource fileSystemResource = new FileSystemResource(destination_file);
        poiExcelWriter.process(new FileSystemResource(sourceFile), fileSystemResource);

        XSSFWorkbook xssfWorkbook = new XSSFWorkbook(fileSystemResource.getInputStream());
        final XSSFSheet sheetAt = xssfWorkbook.getSheetAt(0);

        Assert.assertThat("result file is empty", destination_file.length(), not(0l));
        Assert.assertThat(sheetAt.getPhysicalNumberOfRows(), is(ROWS_TO_GENERATE));
    }