Asserting log messages in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this pytest log assertion?

Consider this pytest test function that asserts a log message is emitted at WARNING level.

PyTest

import logging
import pytest

def func():
    logging.warning("Warning issued")

def test_log_warning(caplog):
    with caplog.at_level(logging.WARNING):
        func()
    assert "Warning issued" in caplog.text

A Test fails with AssertionError

B Test passes (assertion succeeds)

C Test raises a RuntimeError

D Test raises a TypeError

💡 Hint

Check if the log message is captured by caplog at the correct level.

The function emits a WARNING log. The test sets caplog to WARNING level and asserts the message is in caplog.text, so the assertion passes.

❓ assertion

intermediate

Which assertion correctly checks for an ERROR log message using caplog?

You want to assert that the log contains the exact message "Error occurred" at ERROR level.

A assert "Error occurred" in caplog.text and caplog.level == logging.ERROR

B assert caplog.text == "Error occurred" and caplog.records[0].level == logging.ERROR

C assert any(record.levelname == "ERROR" and record.getMessage() == "Error occurred" for record in caplog.records)

D assert caplog.records[0].levelname == "ERROR" and caplog.records[0].msg == "Error occurred"

💡 Hint

caplog.records is a list of log records; check each record's levelname and message.

Option C correctly iterates over all records and checks both levelname and message. Others either check only first record or use wrong attributes.

🔧 Debug

advanced

Why does this pytest log assertion fail unexpectedly?

Given this test code: import logging def func(): logging.info("Info message") def test_log_info(caplog): with caplog.at_level(logging.WARNING): func() assert "Info message" in caplog.text Why does the assertion fail?

A Because caplog.text is empty due to a missing caplog fixture

B Because the log message text is incorrect

C Because logging.info does not produce any log output

D Because caplog is set to WARNING level, INFO messages are not captured

💡 Hint

Check the log level filter set by caplog.at_level.

caplog.at_level(logging.WARNING) filters out messages below WARNING, so INFO messages are ignored and not captured.

❓ framework

advanced

Which pytest fixture is used to capture log messages during tests?

You want to capture and assert log messages emitted by your code in pytest tests. Which fixture should you use?

A caplog

B logfixture

C logcap

D logcapture

💡 Hint

The fixture name starts with 'cap'.

pytest provides the 'caplog' fixture to capture log messages during tests.

🧠 Conceptual

expert

What is the main benefit of asserting log messages in automated tests?

Why do testers assert log messages in their automated test suites?

A To verify that the system reports important events and errors as expected

B To increase test execution speed by skipping functional checks

C To replace UI tests with log checks entirely

D To ensure logs are stored permanently on disk

💡 Hint

Think about why logs are useful in software.

Asserting logs helps confirm that the system reports key events and errors, aiding debugging and monitoring.