Unit test for method containing switch case statement and insert to db

I have a method that contains a switch case block which iterates through an excel file to obtain values to write to a db. I need to write a unit test for this method but I have no idea where to start.
Below is the method of which I need to write the unit test for. If anyone could advise me it would be greatly appreciated.

    public void loadAccount() throws Exception {
    Connection conn = null;
    PreparedStatement insert = null;
    Properties props = new Properties();

    try {
        conn = connMan.allocateConnection();
        conn.setAutoCommit(false);
        insert = conn.prepareStatement(INSERT_SQL_TOP_ACCOUNTS);

        FileInputStream inputStream = new FileInputStream("path");
        props.load(inputStream);
        String excelFilePath = props.getProperty("Account");
        FileInputStream iStream = new FileInputStream(new File(excelFilePath));

        Workbook workbook = new XSSFWorkbook(iStream);
        Sheet firstSheet = workbook.getSheetAt(0);
        Iterator<Row> iterator = firstSheet.iterator();

        // Current date for entry into db
        java.sql.Date sqlDate = new java.sql.Date(System.currentTimeMillis());
        insert.setDate(1, sqlDate);

        // Skips the header row
        iterator.next();

        // Iterate through the first sheet and get the cell values
        while (iterator.hasNext()) {

            Row nextRow = iterator.next();
            Iterator<Cell> cellIterator = nextRow.cellIterator();

            while (cellIterator.hasNext()) {

                Cell cell = cellIterator.next();
                int columnIndex = cell.getColumnIndex();

                switch (columnIndex) {
                case 0:
                    String institution = cell.getStringCellValue();
                    insert.setString(2, institution);
                    break;
                case 1:
                    // Formatting data because of alphanumeric mix in row
                    DataFormatter formatter = new DataFormatter();
                    String dept = formatter.formatCellValue(cell);
                    insert.setString(3, dept);
                    break;
                case 2:
                    int hits = (int) cell.getNumericCellValue();
                    insert.setInt(4, hits);
                    break;
                case 3:
                    int visitors = (int) cell.getNumericCellValue();
                    insert.setInt(5, visitors);
                    break;
                }
            }
            insert.addBatch();
        }
        int[] insertCount = insert.executeBatch();
        int successInserted = 0;
        for (int item : insertCount) {
            if (item == 1) {
                successInserted++;
            }
        }

        log.info("There're " + insertCount.length + " need to be inserted, with successfully [" + successInserted
                + "] inserted");
        conn.commit();          
    } catch (Exception e) {
        log.error("Exception in loadAccount:" + e);
        try {
            conn.rollback();
        } catch (SQLException e1) {
            log.error("Exception when rollback the loading.", e1);
            throw e1;
        }
        throw e;
    } finally {
        connMan.closeStatement(insert);
        try {
            if (conn != null) {
                connMan.deallocateConnection(conn);
            }
        } catch (SQLException e) {
            log.error("Exception in loadAccount:" + e);
            throw e;
        }
    }
}