public void performSortOperation(int option, List<File> pdf) {
        switch (option) {
            case DATE_INDEX:
                sortFilesByDateNewestToOldest(pdf);
                break;
            case NAME_INDEX:
                sortByNameAlphabetical(pdf);
                break;
            case SIZE_INCREASING_ORDER_INDEX:
                sortFilesBySizeIncreasingOrder(pdf);
                break;
            case SIZE_DECREASING_ORDER_INDEX:
                sortFilesBySizeDecreasingOrder(pdf);
                break;
        }
    }
@Test
    public void shouldReturnArraySortedAlphabetically() throws IOException {
        // given
        // (for some reason sorting mocks doesn't work)
        List<String> paths = getPaths();
        mFiles = new ArrayList<>(paths.size());
        for (String item : paths) {
            File f = new File(item);
            f.createNewFile();
            mFiles.add(f);
        }

        File[] expected = new File[]{mFiles.get(5), mFiles.get(3), mFiles.get(4),
                mFiles.get(0), mFiles.get(1), mFiles.get(2)};

        // when
        mInstance.performSortOperation(mInstance.NAME_INDEX, mFiles);

        // then
        Assert.assertEquals(asList(expected), mFiles);
    }