Log level filtering in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this pytest log capture?

Given the following pytest test code with log level filtering, what will be captured in the test log output?

PyTest

import logging

def test_logging(caplog):
    with caplog.at_level(logging.WARNING):
        logging.debug('Debug message')
        logging.warning('Warning message')
        logging.error('Error message')
    print(caplog.text)

A Debug message\nWarning message\nError message\n

B Error message\n

C Warning message\nError message\n

D Debug message\n

💡 Hint

Remember that caplog.at_level sets the minimum log level to capture.

caplog.at_level(logging.WARNING) captures logs with level WARNING and above. DEBUG is below WARNING, so it is not captured.

❓ assertion

intermediate

Which assertion correctly checks that only ERROR logs are captured?

In a pytest test using caplog with level ERROR, which assertion correctly verifies that only ERROR messages are captured?

PyTest

import logging

def test_error_logs_only(caplog):
    with caplog.at_level(logging.ERROR):
        logging.warning('Warning message')
        logging.error('Error message')

A assert caplog.text == 'Warning message\nError message\n'

B assert 'Warning message' not in caplog.text and 'Error message' in caplog.text

C assert caplog.records[0].levelname == 'WARNING'

D assert 'Warning message' in caplog.text and 'Error message' in caplog.text

💡 Hint

Logs below ERROR level should not appear in caplog.text.

Since caplog is set to ERROR level, WARNING messages are not captured. The assertion must confirm WARNING is absent and ERROR is present.

🔧 Debug

advanced

Why does this pytest test fail to capture WARNING logs?

This pytest test intends to capture WARNING logs but fails. What is the cause?

PyTest

import logging

def test_logs(caplog):
    logging.warning('Warning message')
    with caplog.at_level(logging.WARNING):
        pass
    assert 'Warning message' in caplog.text

A The warning log is emitted before caplog.at_level context, so it is not captured.

B caplog.at_level does not capture WARNING logs by default.

C The assertion is incorrect; it should check caplog.records instead of caplog.text.

D Logging is disabled globally, so no logs are captured.

💡 Hint

Consider when the log message is emitted relative to the caplog context.

caplog.at_level only captures logs emitted inside its context. The warning is logged before entering the context, so it is missed.

❓ framework

advanced

How to configure pytest to capture only ERROR logs globally?

Which pytest configuration snippet sets the global log capture level to ERROR for all tests?

A

[pytest]
log_cli = true
log_cli_level = ERROR

B

[pytest]
log_cli = true
log_cli_level = WARNING

C

[pytest]
log_capture = true
log_level = ERROR

D

[pytest]
capture_logs = true
capture_level = ERROR

💡 Hint

Check pytest documentation for log_cli and log_cli_level options.

The correct pytest.ini options to enable live log capture at ERROR level are log_cli=true and log_cli_level=ERROR.

🧠 Conceptual

expert

What is the effect of setting caplog.set_level(logging.INFO) inside a test?

In pytest, what does calling caplog.set_level(logging.INFO) inside a test do?

A It only affects logs emitted before the call to set_level.

B It permanently changes the global logging level for all tests to INFO.

C It disables log capturing for the test.

D It changes the log capture level dynamically for the rest of the test, capturing INFO and above logs.

💡 Hint

Think about how caplog.set_level affects log capturing during test execution.

caplog.set_level changes the capture level dynamically during the test, affecting logs emitted after the call.