Lately, I was studying the concept of unit testing in python, so I have decided to write a imperative strong password validator ( checker ) and also attach a unit test to it.

I would like to know if there is any recommendation for improving this code, Thanks!

main.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-


"""
KhodeNima's unit test learning package. | 23/11/9
"""


import string


ascii_lowercase_letters = string.ascii_lowercase
ascii_uppercase_letters = string.ascii_uppercase
ascii_numbers = string.digits


def is_master_password(literal: str):
    """Chekcs if a string literal have the requirements of a masterpasssword.

    Args:
        string (str): The string literal.

    Raises:
        ValueError: If invalid argument is passed for any parameter.
    """

    if not isinstance(literal, str):
        argument_type = type(literal).__name__
        raise ValueError(f"Invalid argument type passed for the parameter: string | Expected: 'str' | Not: {argument_type}")
    

    allowed_characters = ''.join([ascii_lowercase_letters, ascii_uppercase_letters, ascii_numbers])
    min_password_length = 5
    max_password_length = 20
    string_length = len(literal)
    valid_characters_count = 0

    has_upper_case = False
    has_lower_case = False
    has_digit = False
    

    if string_length < min_password_length:
        return False

    if string_length > max_password_length:
       return False


    for character in literal:

        if character in allowed_characters:
            valid_characters_count += 1


    for character in literal:

        if all([has_digit, has_upper_case, has_lower_case]):
            break
        
        if character.isdigit():
            has_digit = True
        
        if character.isupper():
            has_upper_case = True

        if character.islower():
            has_lower_case = True

        

    if not valid_characters_count == string_length or not all([has_digit, has_lower_case, has_upper_case]):
        return False
    
    return True



print(is_master_password("Reedwolf13"))

unit_test.py

"""
KhodeNima's Unit test training package | 2023/11/9
"""


import unittest
from main import (
    is_master_password
)


class MasterPasswordExaminerTest(unittest.TestCase):
    """
    The main program test case
    """

    def test_character_validation_check(self):
        """Does the program character checking system work correctly?
        """

        self.assertEqual(is_master_password("!-*&%#@$()"), False)
        self.assertEqual(is_master_password('Redwolf1'), True)

    def test_length_validation_check(self):
        """Does the program validate the password length correctly?
        """

        self.assertEqual(is_master_password('Jsf3'), False)
        self.assertEqual(is_master_password('mnbRDSAQOPJK123986532nm'), False)

    def test_requirement_check(self):
        """Does the program validates the password requirements correcly? (1 Uppercase L, 1 Lowercase L, 1 Digit)
        """

        self.assertEqual(is_master_password("Redwolf1"), True)
        self.assertEqual(is_master_password("Redwolf"), False)
        self.assertEqual(is_master_password("redwolf1"), False)




if __name__ == '__main__':
    unittest.main()

```