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 shouldThrowOnInvalidSortOption() {
        // given
        List<Integer> invalidOptions = asList(-1, 14, 65535, 8);

        for (Integer item : invalidOptions) {
            try {
                // when
                mInstance.performSortOperation(item, mFiles);
            } catch (IllegalArgumentException ex) {
                // then
                Assert.assertTrue(ex.getMessage().startsWith("Invalid sort option"));
            }
        }
    }