Asserting exceptions (pytest.raises) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ assertion

intermediate

Correct use of pytest.raises to catch ZeroDivisionError

What will be the result of this test when run with pytest?

PyTest

import pytest

def test_divide_by_zero():
    with pytest.raises(ZeroDivisionError):
        x = 1 / 0

A Test passes because ZeroDivisionError is correctly caught

B Test fails because ZeroDivisionError is not caught

C Test raises a SyntaxError due to incorrect pytest usage

D Test fails because the exception type is wrong

💡 Hint

Remember pytest.raises expects the exact exception type to catch.

The test uses pytest.raises with ZeroDivisionError, which matches the exception raised by dividing by zero, so the test passes.

❓ assertion

intermediate

Detecting wrong exception type in pytest.raises

What happens when this test runs?

PyTest

import pytest

def test_value_error():
    with pytest.raises(KeyError):
        int('abc')

A Test fails because ValueError is raised, not KeyError

B Test passes because any exception is accepted

C Test raises a TypeError due to wrong exception type

D Test passes because KeyError is raised

💡 Hint

Check which exception int('abc') actually raises.

int('abc') raises ValueError, but pytest.raises expects KeyError, so the test fails.

❓ Predict Output

advanced

Output of pytest.raises context manager with exception info

What will be the value of 'exc_type' after running this test?

PyTest

import pytest

def test_exception_info():
    with pytest.raises(ValueError) as exc_info:
        raise ValueError('Invalid input')
    exc_type = exc_info.type
    print(exc_type.__name__)

A None

B KeyError

C ValueError

D TypeError

💡 Hint

exc_info.type holds the exception class caught by pytest.raises.

The exception raised is ValueError, so exc_info.type is ValueError.

🔧 Debug

advanced

Why does this pytest.raises test fail unexpectedly?

Identify why this test fails even though it seems to catch the exception.

PyTest

import pytest

def test_key_error():
    with pytest.raises(KeyError):
        d = {'a': 1}
        value = d['b']
        print('Accessed value:', value)

A Test fails because print statement is outside the with block

B Test fails because KeyError is not raised inside the with block

C Test fails because print statement executes after exception and causes error

D Test passes because KeyError is raised inside the with block

💡 Hint

Check where the exception is raised and if the with block covers it.

The KeyError is raised when accessing d['b'], which is inside the with block, so pytest.raises catches it and the test passes.

❓ framework

expert

Using pytest.raises to assert exception message content

Which option correctly asserts that the exception message contains the word 'timeout'?

PyTest

import pytest

def test_timeout_error():
    with pytest.raises(RuntimeError) as exc_info:
        raise RuntimeError('Connection timeout occurred')
    # Assertion here

A assert exc_info.value.message == 'timeout'

B assert 'timeout' in str(exc_info.value)

C assert exc_info.type == 'timeout'

D assert exc_info.message.contains('timeout')

💡 Hint

Exception message is accessed via str(exc_info.value).

The exception message is a string representation of exc_info.value, so checking 'timeout' in str(exc_info.value) is correct.