How to pass a string variable from one function to another?

I am trying to pass the test result from my test1 and test2 function, to the save_results function, so I can write the result to an Excel file, how should I change my code to achieve that?

import os
import xlswriter
from datetime import datetime
import time


def save_results():
    os.chdir(r'C:\Users\user\Documents\Results')
    workbook = xlsxwriter.Workbook(datetime_output_results+'.xlsx')
    worksheet = workbook.add_worksheet()
    bold = workbook.add_format({'bold': True})
    worksheet.set_column('A:A', 20)
    worksheet.write('A1', 'here i would like to write the test1 result')
    #worksheet.write('B1','here i would like to write the test2 result')
    workbook.close()


def test1():
    output = str(ser.read(1000).decode())
    output = str(output)
    if "0x1" in output :
        print('Pass')
        return 'Pass'
    else:
        print('Fail')
        return 'Fail'


def test2():
    output2 = str(ser.read(1000).decode())
    print(output2)
    test2_output = str(output2)
    if "0x1" in test2_output:
        print('Pass')
        return 'Pass'
    else:
        print('Fail')
        return 'Fail'

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