caplog for log messages in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to capture log messages using caplog.

PyTest

def test_logging(caplog):
    with caplog.at_level([1]):
        logger = logging.getLogger('test')
        logger.info('Test message')
    assert 'Test message' in caplog.text

Drag options to blanks, or click blank then click option'

Alogging.INFO

Blogging.DEBUG

Clogging.ERROR

Dlogging.WARNING

Attempts:

3 left

💡 Hint

Common Mistakes

Using a logging level higher than INFO will not capture the info message.

Not using caplog.at_level context manager.

The caplog.at_level() context manager sets the logging level to capture messages. logging.INFO captures info level logs.

2fill in blank

medium

Complete the code to check the first captured log message's level name.

PyTest

def test_log_level_name(caplog):
    logger = logging.getLogger('test')
    logger.error('Error occurred')
    assert caplog.records[0].[1] == 'ERROR'

Drag options to blanks, or click blank then click option'

Alevelname

Blevelno

Cmsg

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using levelno which is a number, not a string.

Using msg which is the message text.

The levelname attribute of a log record gives the level as a string like 'ERROR'.

3fill in blank

hard

Fix the error in the code to capture debug messages with caplog.

PyTest

def test_debug_log(caplog):
    with caplog.at_level([1]):
        logger = logging.getLogger('test')
        logger.debug('Debug info')
    assert 'Debug info' in caplog.text

Drag options to blanks, or click blank then click option'

Alogging.INFO

Blogging.ERROR

Clogging.DEBUG

Dlogging.CRITICAL

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the level to INFO or higher will miss debug messages.

Not using caplog.at_level context manager.

Debug messages require the logging level to be set to logging.DEBUG or lower to be captured.

4fill in blank

hard

Fill both blanks to filter captured logs by level and check message content.

PyTest

def test_filter_logs(caplog):
    logger = logging.getLogger('test')
    logger.warning('Warning message')
    logger.error('Error message')
    filtered = [record for record in caplog.records if record.[1] == [2]]
    assert any('Warning' in record.msg for record in filtered)

Drag options to blanks, or click blank then click option'

Alevelname

Blevelno

C'WARNING'

Dlogging.WARNING

Attempts:

3 left

💡 Hint

Common Mistakes

Using levelno but comparing to a string.

Comparing levelname to a numeric constant.

To filter by level name, use levelname and compare to the string 'WARNING'.

5fill in blank

hard

Fill all three blanks to capture logs at error level, check message count, and verify message text.

PyTest

def test_error_logs_count(caplog):
    with caplog.at_level([1]):
        logger = logging.getLogger('test')
        logger.error('First error')
        logger.error('Second error')
    errors = [record for record in caplog.records if record.[2] == [3]]
    assert len(errors) == 2
    assert errors[0].msg == 'First error'

Drag options to blanks, or click blank then click option'

Alogging.ERROR

Blevelname

C'ERROR'

Dlevelno

Attempts:

3 left

💡 Hint

Common Mistakes

Using numeric level levelno but comparing to string.

Setting capture level too high or too low.

Set capture level to logging.ERROR. Filter records by levelname equal to 'ERROR'.

Practice

1. What is the main purpose of using caplog in pytest tests?

easy

A. To capture and check log messages generated during test execution

B. To mock external API calls in tests

C. To measure test execution time

D. To generate test reports automatically

Solution

1. Step 1: Understand caplog's role in pytest

   caplog is a pytest fixture used to capture log messages during tests.

2. Step 2: Identify the main use

   It allows assertions on log output to verify correct logging behavior.

3. Final Answer:

   To capture and check log messages generated during test execution -> Option A

4. Quick Check:

   caplog = capture logs [OK]

Hint: caplog captures logs so you can check messages easily [OK]

Common Mistakes:

• Confusing caplog with mocking tools
• Thinking caplog measures time
• Assuming caplog generates reports

2. Which of the following is the correct way to use caplog to capture only WARNING level logs in a test function?

easy

A. caplog.log_level(logging.WARNING)

B. caplog.set_level(logging.WARNING)

C. caplog.capture_level = logging.WARNING

D. with caplog.at_level(logging.WARNING):

Solution

1. Step 1: Recall caplog syntax for setting log level

   caplog uses a context manager method at_level() to set the log level temporarily.

2. Step 2: Match correct syntax

   The correct syntax is with caplog.at_level(logging.WARNING): to capture warnings.

3. Final Answer:

   with caplog.at_level(logging.WARNING): -> Option D

4. Quick Check:

   Use caplog.at_level() for log level [OK]

Hint: Use with caplog.at_level(level) to set capture level [OK]

Common Mistakes:

• Trying to set level by assignment
• Using non-existent caplog methods
• Forgetting to use 'with' for context

3. Given the following test code, what will be the output of the assertion?

import logging

def test_log_message(caplog):
    with caplog.at_level(logging.INFO):
        logging.info('Test started')
    assert 'Test started' in caplog.text

medium

A. The assertion passes because the log message is captured

B. The assertion fails because caplog.text is empty

C. The test raises a NameError due to missing import

D. The assertion fails because logging level is too low

Solution

1. Step 1: Analyze log capture level

   The code sets caplog to capture INFO level logs, which includes the info message logged.

2. Step 2: Check assertion on caplog.text

   The message 'Test started' is logged and appears in caplog.text, so the assertion passes.

3. Final Answer:

   The assertion passes because the log message is captured -> Option A

4. Quick Check:

   Logged message in caplog.text = assertion pass [OK]

Hint: caplog.text holds captured logs as a string [OK]

Common Mistakes:

• Assuming caplog.text is empty without at_level
• Confusing log levels and capture
• Forgetting to import logging

4. Identify the error in the following pytest test using caplog:

import logging

def test_error_log(caplog):
    caplog.at_level(logging.ERROR)
    logging.error('An error occurred')
    assert 'An error occurred' in caplog.text

medium

A. logging.error() is called before caplog is imported

B. caplog.at_level() must be used as a context manager with 'with'

C. assertion should check caplog.records instead of caplog.text

D. logging level ERROR is too high to capture

Solution

1. Step 1: Check usage of caplog.at_level()

   caplog.at_level() is a context manager and must be used with 'with' keyword.

2. Step 2: Identify missing 'with' statement

   The code calls caplog.at_level() without 'with', so it does not set the level properly.

3. Final Answer:

   caplog.at_level() must be used as a context manager with 'with' -> Option B

4. Quick Check:

   Use 'with caplog.at_level()' not just call [OK]

Hint: Always use 'with' for caplog.at_level() context [OK]

Common Mistakes:

• Calling caplog.at_level() without 'with'
• Checking wrong caplog attribute
• Misunderstanding log level capture

5. You want to test that your function logs a WARNING message only when a certain condition is true. Which pytest test code correctly uses caplog to check this behavior?

hard

A. def test_warn_log(caplog):
with caplog.at_level(logging.WARNING):
my_function(True)
assert 'Warning triggered' in caplog.text
with caplog.at_level(logging.WARNING):
my_function(False)
assert 'Warning triggered' not in caplog.text

B. def test_warn_log(caplog):
with caplog.at_level(logging.INFO):
my_function(True)
assert 'Warning triggered' in caplog.text

C. def test_warn_log(caplog):
with caplog.at_level(logging.WARNING):
my_function(True)
my_function(False)
assert caplog.text.count('Warning triggered') == 1

D. def test_warn_log(caplog):
caplog.set_level(logging.WARNING)
my_function(True)
assert 'Warning triggered' in caplog.text
my_function(False)
assert 'Warning triggered' not in caplog.text

Solution

1. Step 1: Understand the requirement

   We want to check that the warning message logs only once when condition is true, not when false.

2. Step 2: Analyze options for correct caplog usage

   def test_warn_log(caplog): with caplog.at_level(logging.WARNING): my_function(True) my_function(False) assert caplog.text.count('Warning triggered') == 1 uses one context capturing both calls and asserts the warning appears exactly once, matching the requirement.

3. Step 3: Why other options fail

   def test_warn_log(caplog): with caplog.at_level(logging.WARNING): my_function(True) assert 'Warning triggered' in caplog.text with caplog.at_level(logging.WARNING): my_function(False) assert 'Warning triggered' not in caplog.text: separate contexts but caplog.text accumulates logs, so second assert 'Warning triggered' not in caplog.text fails (message from first call persists); def test_warn_log(caplog): caplog.set_level(logging.WARNING) my_function(True) assert 'Warning triggered' in caplog.text my_function(False) assert 'Warning triggered' not in caplog.text: caplog.set_level does not exist (AttributeError), and accumulation would fail second assert; def test_warn_log(caplog): with caplog.at_level(logging.INFO): my_function(True) assert 'Warning triggered' in caplog.text: tests only True case with INFO level (captures WARNING but no False verification).

4. Final Answer:

   def test_warn_log(caplog): with caplog.at_level(logging.WARNING): my_function(True) my_function(False) assert caplog.text.count('Warning triggered') == 1 -> Option C

5. Quick Check:

   Use one caplog context and count messages [OK]

Hint: Use one with caplog.at_level() block and count messages [OK]

Common Mistakes:

• Using multiple caplog contexts losing logs
• Using wrong log level in at_level
• Assuming caplog.set_level exists