Infinite loop testing

How could I test an infinite loop?
For example:

func.py

def func():
    while True:
        char = input().lower()
        if char == 'q':
            break 
        elif char.isalpha():
            print("It's not a number")
        if int(char) == #some_number
            break
        else:
            print('Try again')
        

test.py

def test_func():
    ???

Is there any solution for testing this?

>Solution :

You can use unittest to mock the user’s input:

import builtins
from unittest.mock import patch

def func():
    while True:
        char = input().lower()
        if char == 'q':
            break 
        elif char.isalpha():
            print("It's not a number")
        if int(char) == 3:
            break
        else:
            print('Try again')

def test_func(inputs):
    with patch("builtins.input") as input_mock:
        input_mock.side_effect = inputs
        func()

test_func(["q"])
test_func(["3"])  
test_func(["4", "5", "6"])  # StopIteration error indicates this input is not sufficient for the function to return
test_func(["a", "b", "c", "q"])  # ValueError indicates a bug in the function
test_func(["4", "5", "6", "q"])  # Try again 3 times as expected