Checking exception attributes in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of checking exception attributes in pytest?

To verify not only that an exception is raised but also that its details, like message or error code, are correct.

beginner

How do you capture an exception in pytest to check its attributes?

Use the 'with pytest.raises(ExceptionType) as exc_info:' syntax to capture the exception object in 'exc_info'.

intermediate

Given this code snippet, what does 'exc_info.value' represent?

with pytest.raises(ValueError) as exc_info:
    raise ValueError('Invalid input')

'exc_info.value' is the actual exception instance raised, allowing access to its attributes like message.

intermediate

How can you check the message of a raised exception in pytest?

After capturing the exception, use 'str(exc_info.value)' or 'exc_info.value.args' to check the message content.

intermediate

Why is it better to check exception attributes instead of just the exception type?

Because different errors of the same type can have different causes; checking attributes ensures the exact error scenario is tested.

Which pytest syntax captures an exception to check its attributes?

A catch ExceptionType as exc_info:

B try: except ExceptionType as exc_info:

C with pytest.raises(ExceptionType) as exc_info:

D assertRaises(ExceptionType)

The 'with pytest.raises(ExceptionType) as exc_info:' syntax captures the exception for attribute checks.

How do you access the message of a captured exception in pytest?

A str(exc_info.value)

B exc_info.message

C exc_info.args[0]

D exc_info.value.message

Use 'str(exc_info.value)' or 'exc_info.value.args[0]' to get the exception message.

What does 'exc_info.value' represent in pytest exception checking?

A The exception type

B The test result

C The test function

D The exception instance raised

'exc_info.value' is the actual exception instance raised during the test.

Why should you check exception attributes in tests?

A To avoid writing assertions

B To confirm the exact error details, not just the type

C To speed up test execution

D To ignore error messages

Checking attributes ensures the test verifies the precise error scenario.

Which of these is NOT a valid way to check exception attributes in pytest?

A assert exc_info.message == 'error'

B assert exc_info.value.args[0] == 'message'

C assert 'error' in str(exc_info.value)

D assert isinstance(exc_info.value, ExceptionType)

'exc_info' does not have a 'message' attribute; use 'exc_info.value' instead.

Explain how to check the message of a raised exception using pytest.

Think about capturing the exception and then reading its message.

Why is it important to check exception attributes in your tests, not just the exception type?

Consider how different errors can have the same type but different meanings.