Testing exception chains in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check that a ValueError is raised.

PyTest

import pytest

def test_value_error():
    with pytest.raises([1]):
        int('abc')

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

AKeyError

BValueError

CTypeError

DIndexError

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong exception type like TypeError or KeyError.

Not using pytest.raises context manager.

The int('abc') call raises a ValueError because 'abc' cannot be converted to an integer.

2fill in blank

medium

Complete the code to check that a KeyError is raised with the correct message.

PyTest

import pytest

def test_key_error():
    with pytest.raises(KeyError) as exc_info:
        {}['missing']
    assert exc_info.value.args[0] == [1]

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

A"key"

B"missing"

C'key'

D'missing'

Attempts:

3 left

💡 Hint

Common Mistakes

Using double quotes instead of single quotes (both work but be consistent).

Checking the wrong attribute of exc_info.

The KeyError message is the missing key as a string. It is stored in exc_info.value.args[0].

3fill in blank

hard

Fix the error in the test to correctly check the exception chain.

PyTest

import pytest

def test_exception_chain():
    with pytest.raises(RuntimeError) as exc_info:
        try:
            int('abc')
        except ValueError as e:
            raise RuntimeError('Failed') from [1]

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

Ae

Bexc_info

CRuntimeError

DValueError

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable name in the 'from' clause.

Using the exception class instead of the instance.

The from keyword requires the original exception instance, which is e here.

4fill in blank

hard

Fill both blanks to assert the original exception type and message in the exception chain.

PyTest

import pytest

def test_exception_chain_details():
    with pytest.raises(RuntimeError) as exc_info:
        try:
            int('abc')
        except ValueError as e:
            raise RuntimeError('Failed') from e
    original = exc_info.value.__cause__
    assert isinstance(original, [1])
    assert str(original) == [2]

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

AValueError

BTypeError

C'invalid literal for int() with base 10: \'abc\''

D'Failed'

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing the RuntimeError message with the original exception message.

Using the wrong exception type in isinstance check.

The original exception is a ValueError with the message about invalid literal.

5fill in blank

hard

Fill all three blanks to write a test that verifies the exception chain and message.

PyTest

import pytest

def test_full_exception_chain():
    with pytest.raises([1]) as exc_info:
        try:
            float('xyz')
        except [2] as e:
            raise [3]('Conversion failed') from e

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

ARuntimeError

BValueError

DTypeError

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up exception types in the raises or except clauses.

Not using the 'from' keyword to chain exceptions.

The test expects a RuntimeError raised from a caught ValueError when converting 'xyz' to float.