pytest.raises context manager - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the pytest.raises context manager?

It is used to check that a specific exception is raised during the execution of a block of code in a test.

beginner

How do you use pytest.raises to test if a function raises a ValueError?

Use it as a context manager like this:<br>

with pytest.raises(ValueError):
    function_that_raises()

beginner

What happens if the expected exception is not raised inside the pytest.raises block?

The test will fail because pytest.raises expects the specified exception to occur.

intermediate

Can pytest.raises capture the exception object for further checks?

Yes, by using the as keyword, you can capture the exception and inspect its message or attributes.<br>Example:<br>

with pytest.raises(ValueError) as exc_info:
    function_that_raises()
assert 'error message' in str(exc_info.value)

intermediate

Why is using pytest.raises better than a try-except block in tests?

Because it makes tests cleaner and more readable by clearly showing the expected exception, and it automatically fails the test if the exception is not raised.

What does pytest.raises(ValueError) check for?

A That the test passes without errors

B That no exceptions are raised

C That the function returns a ValueError

D That a ValueError exception is raised inside the block

pytest.raises(ValueError) expects a ValueError exception to be raised inside its block.

How do you capture the exception object with pytest.raises?

A pytest.raises(Exception).catch()

B with pytest.raises(Exception).capture():

C with pytest.raises(Exception) as exc_info:

D with pytest.capture(Exception) as exc_info:

Use as exc_info to capture the exception object for inspection.

What happens if the expected exception is not raised inside pytest.raises?

A The test is skipped

B The test fails

C The test passes

D The test raises a warning

If the expected exception is not raised, pytest.raises causes the test to fail.

Which of these is a correct way to test that my_func() raises a KeyError?

A with pytest.raises(KeyError): my_func()

B pytest.raises(KeyError, my_func())

C try: my_func() except KeyError: pass

D assert my_func() raises KeyError

The correct syntax uses with pytest.raises(KeyError): as a context manager.

Why is pytest.raises preferred over manual try-except in tests?

A It makes tests clearer and automatically fails if exception is missing

B It runs tests faster

C It catches all exceptions silently

D It disables exceptions

pytest.raises improves readability and test reliability by clearly expecting exceptions.

Explain how to use pytest.raises to test that a function raises a specific exception and how to check the exception message.

Think about capturing the exception and then asserting on its message.

Describe what happens when the expected exception is not raised inside a pytest.raises block during test execution.

Consider the purpose of expecting exceptions in tests.