Why error path testing ensures robustness in PyTest - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the function raises a ValueError for invalid input.

PyTest

import pytest

def test_invalid_input():
    with pytest.raises([1]):
        process_data('bad_input')

Drag options to blanks, or click blank then click option'

ATypeError

BValueError

CKeyError

DIndexError

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong exception type in pytest.raises.

Not using pytest.raises at all.

The test checks that process_data raises a ValueError when given bad input, which is a common error path to test for robustness.

2fill in blank

medium

Complete the assertion to verify the error message contains the word 'invalid'.

PyTest

import pytest

def test_error_message():
    with pytest.raises(ValueError) as excinfo:
        process_data('bad_input')
    assert '[1]' in str(excinfo.value)

Drag options to blanks, or click blank then click option'

A'invalid'

B'error'

C'fail'

D'exception'

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for a wrong or unrelated word in the error message.

Not converting the exception to string before checking.

The assertion checks that the error message includes the word 'invalid', confirming the error path is correctly triggered.

3fill in blank

hard

Fix the error in the test that tries to catch a KeyError but the function raises ValueError.

PyTest

import pytest

def test_wrong_exception():
    with pytest.raises([1]):
        process_data('bad_input')

Drag options to blanks, or click blank then click option'

AValueError

BTypeError

CKeyError

DRuntimeError

Attempts:

3 left

💡 Hint

Common Mistakes

Expecting the wrong exception type.

Not updating the test after function changes.

The function raises a ValueError, so the test must expect that exception to pass.

4fill in blank

hard

Fill both blanks to test that the function raises a TypeError when input is not a string and the error message contains 'type'.

PyTest

import pytest

def test_type_error():
    with pytest.raises([1]) as excinfo:
        process_data(123)
    assert '[2]' in str(excinfo.value)

Drag options to blanks, or click blank then click option'

ATypeError

BValueError

Ctype

Dinvalid

Attempts:

3 left

💡 Hint

Common Mistakes

Using ValueError instead of TypeError.

Checking for 'invalid' instead of 'type' in the message.

The test expects a TypeError when input is not a string, and checks the error message contains 'type' to confirm the cause.

5fill in blank

hard

Fill all three blanks to create a test that asserts a KeyError is raised when a missing key is accessed, and the error message contains the missing key name.

PyTest

import pytest

def test_missing_key():
    with pytest.raises([1]) as excinfo:
        data = {'a': 1}
        value = data[[2]]
    assert [3] in str(excinfo.value)

Drag options to blanks, or click blank then click option'

AKeyError

B'b'

DValueError

Attempts:

3 left

💡 Hint

Common Mistakes

Using ValueError instead of KeyError.

Not using quotes around the missing key in the assertion.

The test expects a KeyError when accessing a missing key 'b', and checks the error message includes 'b' to confirm the missing key.