import unittest

class TestUserRegistration(unittest.TestCase):
    
    def test_username_validation(self):
        # Valid equivalence classes for username
        valid_usernames = ["user123", "username", "testuser", "123456789012"]
        # Invalid equivalence classes for username
        invalid_usernames = ["u", "user1234567890", "username1234567890"]

        for username in valid_usernames:
            self.assertTrue(validate_username(username))
        
        for username in invalid_usernames:
            self.assertFalse(validate_username(username))
    
    def test_password_validation(self):
        # Valid equivalence classes for password
        valid_passwords = ["Password1", "SecurePwd123", "12345678aA", "Abcdefg12345678"]
        # Invalid equivalence classes for password
        invalid_passwords = ["password", "12345678", "Abcdefghijklmnop", "12345678901234567"]

        for password in valid_passwords:
            self.assertTrue(validate_password(password))
        
        for password in invalid_passwords:
            self.assertFalse(validate_password(password))

# Function to validate username
def validate_username(username):
    # Check if username length is between 6 to 12 characters
    if 6 <= len(username) <= 12:
        return True
    else:
        return False

# Function to validate password
def validate_password(password):
    # Check if password length is between 8 to 16 characters
    if not (8 <= len(password) <= 16):
        return False
    # Check if password contains both letters and numbers
    has_digit = any(char.isdigit() for char in password)
    has_alpha = any(char.isalpha() for char in password)
    if has_digit and has_alpha:
        return True
    else:
        return False

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