import unittest
import importlib

def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)

class TestRegisterUser(unittest.TestCase):
    def setUp(self):
        """Reset users_db before each test"""
        import user_code
        user_code.users_db.clear()

    def test_successful_registration(self):
        """Checks that a user is successfully registered with valid data"""
        import user_code
        try:
            result = user_code.register_user(username="Alice", email="alice@example.com", age=18)
            expected_output = "User Alice registered successfully!"
            condition = result == expected_output
            failure_message = f"For input `('Alice', 'alice@example.com', 18)`, expected `{expected_output}`, but got `{result}`."
        
        except AttributeError:
            condition = False
            failure_message = "The function `register_user` is not defined."
        
        _dynamic_test(self, condition, "The `register_user` function registers a user correctly.", failure_message)
    
    def test_user_count_after_registration(self):
        """Checks that the number of users in the database is correct after a successful registration"""
        import user_code
        try:
            user_code.register_user(username="Alice", email="alice@example.com", age=18)
            condition = len(user_code.users_db) == 1
            failure_message = f"For input `('Alice', 'alice@example.com', 18)`, expected 1 user in the database, but found {len(user_code.users_db)}."
        
        except AttributeError:
            condition = False
            failure_message = "The function `register_user` is not defined."
        
        _dynamic_test(self, condition, "The number of registered users is correct.", failure_message)
    
    def test_user_data_after_registration(self):
        """Checks that the user data is correctly added to the database after a successful registration"""
        import user_code
        try:
            user_code.register_user(username="Alice", email="alice@example.com", age=18)
            registered_user = user_code.users_db[0]
            condition = (registered_user["username"] == "Alice" and
                         registered_user["email"] == "alice@example.com" and
                         registered_user["age"] == 18)
            failure_message = f"For input `('Alice', 'alice@example.com', 18)`, expected user data `{{'username': 'Alice', 'email': 'alice@example.com', 'age': 18}}` in `users_db`, but got {registered_user}."
        
        except AttributeError:
            condition = False
            failure_message = "The function `register_user` is not defined."
        except Exception:
            condition = False
            failure_message = "For input `('Alice', 'alice@example.com', 18)`, expected user data `{{'username': 'Alice', 'email': 'alice@example.com', 'age': 18}}` in `users_db`, but this element won't be found there."
        
        _dynamic_test(self, condition, "The user data is correctly stored in the database.", failure_message)
    
    def test_underage_registration(self):
        """Checks that users under 18 cannot register"""
        import user_code
        try:
            result = user_code.register_user(username="Bob", email="bob@example.com", age=16)
            expected_output = "Registration failed: age must be 18 or older."
            condition = result == expected_output and len(user_code.users_db) == 0
            failure_message = f"For input `('Bob', 'bob@example.com', 16)`, expected `{expected_output}`, but got `{result}`."
        
        except AttributeError:
            condition = False
            failure_message = "The function `register_user` is not defined."
        
        _dynamic_test(self, condition, "The `register_user` function correctly blocks underage users.", failure_message)
    
    def test_multiple_registrations(self):
        """Checks that multiple users can be registered"""
        import user_code
        try:
            user_code.register_user(username="Alice", email="alice@example.com", age=18)
            user_code.register_user(username="Charlie", email="charlie@example.com", age=30)
            condition = len(user_code.users_db) == 2
            failure_message = f"For input registrations `('Alice', 'alice@example.com', 18)` and `('Charlie', 'charlie@example.com', 30)`, expected 2 users, but found {len(user_code.users_db)}."
        
        except AttributeError:
            condition = False
            failure_message = "The function `register_user` is not defined."
        
        _dynamic_test(self, condition, "The `register_user` function allows multiple users to register.", failure_message)

    def test_users_db_is_declared(self):
        import user_code
        _dynamic_test(
            self,
            hasattr(user_code, 'users_db'),
            "The `users_db` variable is declared.",
            "Expected `users_db` to be declared."
        )

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

test_main.py

Gain a solid understanding of how functions shape Python programming. Master defining and calling functions, working with arguments, handling return values, and creating flexible, efficient code using recursion and lambda expressions.

Explore what functions are and why they're essential in Python. Learn how to create functions, define arguments, handle return values, and use built-in functions effectively.

Learn how positional and optional arguments work in Python. Build adaptable functions that handle different inputs and improve flexibility in your code.

Understand how to work with arbitrary and keyword arguments to handle variable input sizes. Learn how these techniques make your functions more dynamic and organized.

Discover how return values represent a function's output. Learn to return single or multiple values, use None, and explore generators for more advanced data flow control.

Unlock advanced function concepts with recursion and lambda functions. Learn how recursion solves repetitive problems and how lambda expressions create concise, one-line functions.

Challenge: Positional Arguments

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Challenge: Positional Arguments

Solution