Function Returns Expected Output

Validates that a function works as expected (correct output or correct exception).

Location of the snippet: python/basics/functions/function_returns_expected_output

This snippet is used to validate that a function works as expected (correct output or correct exception).

Device Type
Jupyter

Variables:

Variable Name	Variable Description	Type	Required?	Default
function_name	Name of the function to be tested.	str	Yes
test_cases	List of dictionaries with keys 'args', 'kwargs', 'return_value', 'exception', 'exception_message' for each test case.	list	Yes

Examples:

1. Basic Function - Sum of Two Numbers

This example tests a simple function that adds two numbers, checking for a specific return value.

Scenario: Students are tasked with writing a function add_numbers that takes two arguments and returns their sum.

Task: Define a Python function named add_numbers(a, b) that returns the sum of a and b.

Placeholder:

def add_numbers(a, b):
    pass

Solution:

def add_numbers(a, b):
    return a + b

Snippet for the assertion:

Variable Name	Value
function_name	add_numbers
test_cases	[{"args": (1, 2), "return_value": 3}, {"args": (10, 20), "return_value": 30}]

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2. Function with Keyword Arguments and String Output

This example demonstrates testing a function that uses keyword arguments and returns a string.

Scenario: Students need to write a function greet_user that takes a name (positional) and an optional greeting (keyword) and returns a formatted greeting string.

Task: Define a Python function named greet_user(name, greeting="Hello") that returns a string like "greeting, name!".

Placeholder:

def greet_user(name, greeting="Hello"):
    pass

Solution:

def greet_user(name, greeting="Hello"):
    return f"{greeting}, {name}!"

Snippet for the assertion:

Variable Name	Value
function_name	greet_user
test_cases	[{"args": ("Alice", ), "return_value": "Hello, Alice!"}, {"args": ("Bob", ), "kwargs": {"greeting": "Hi"}, "return_value": "Hi, Bob!"}]

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3. Function Expected to Raise an Exception (Test only Exception, not Exception Message)

This example shows how to test if a function correctly raises a specific type of exception.

Scenario: Students are to write a function divide_numbers that performs division but raises a ZeroDivisionError if the divisor is zero.

Task: Define a Python function divide_numbers(numerator, denominator) that returns numerator / denominator. If denominator is 0, it should raise a ZeroDivisionError.

Placeholder:

def divide_numbers(numerator, denominator):
    pass

Solution:

def divide_numbers(numerator, denominator):
    if denominator == 0:
        raise ZeroDivisionError("Cannot divide by zero.")
    return numerator / denominator

Snippet for the assertion:

Variable Name	Value
function_name	divide_numbers
test_cases	[{"args": (10, 2), "return_value": 5.0}, {"args": (10, 0), "exception": ZeroDivisionError}]

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4. Function Expected to Raise an Exception with a Specific Message

This example shows how to test if a function raises a specific exception with a specific message.

Scenario: Students are to write a function greet_user that greets a user by name but raises a ValueError with a specific message if the name is empty.

Task: Define a Python function greet_user(name) that returns "Hello, " + name. If name is an empty string, it should raise a ValueError with the message "Name cannot be empty.".

Placeholder:

def greet_user(name):
    pass

Solution:

def greet_user(name):
    if not name:
        raise ValueError("Name cannot be empty.")
    return "Hello, " + name

Snippet for the assertion:

Variable Name	Value
function_name	greet_user
test_cases	[{"args": ("Alice",), "return_value": "Hello, Alice"}, {"args": ("",), "exception": ValueError, "exception_message": "Name cannot be empty."}]

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