Asserting log messages in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to capture log messages using pytest.

PyTest

def test_log_capture(caplog):
    with caplog.[1](level="INFO"):
        logger = logging.getLogger()
        logger.info("Hello")

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

Acapture

Bset_level

Clog

Dat_level

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method that does not exist on caplog.

Trying to capture logs without setting the level.

The caplog.at_level() method sets the logging level to capture messages at or above that level.

2fill in blank

medium

Complete the code to assert that a log message contains the expected text.

PyTest

def test_log_message(caplog):
    with caplog.at_level("WARNING"):
        logger = logging.getLogger()
        logger.warning("Disk space low")
    assert "[1]" in caplog.text

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

Adebug

BDisk space low

Cinfo

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for a log level name instead of the message.

Using a wrong string that does not appear in logs.

The caplog.text contains all captured log messages as a single string. We check if the expected message is present.

3fill in blank

hard

Fix the error in the assertion to check the first captured log record's message.

PyTest

def test_first_log_message(caplog):
    with caplog.at_level("ERROR"):
        logger = logging.getLogger()
        logger.error("Failure occurred")
    assert caplog.records[0].[1] == "Failure occurred"

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

Amsg

Bmessage

Ctext

Dlog

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'message' instead of 'msg' attribute.

Trying to access a non-existent attribute.

The LogRecord object has a msg attribute that stores the log message.

4fill in blank

hard

Fill both blanks to assert that the log level of the first record is ERROR and the message contains 'critical'.

PyTest

def test_log_level_and_message(caplog):
    with caplog.at_level("ERROR"):
        logger = logging.getLogger()
        logger.error("A critical failure happened")
    assert caplog.records[0].[1] == logging.[2]
    assert "critical" in caplog.records[0].msg

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

Alevelno

Blevelname

CERROR

DCRITICAL

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'levelname' which is a string, not numeric.

Using 'CRITICAL' constant instead of 'ERROR'.

The levelno attribute holds the numeric log level. logging.ERROR is the constant for the ERROR level.

5fill in blank

hard

Fill all three blanks to capture logs at INFO level, log an info message, and assert the message is captured.

PyTest

def test_info_log_capture(caplog):
    with caplog.[1]("INFO"):
        logger = logging.getLogger()
        logger.[2]("Process started")
    assert "[3]" in caplog.text

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

Aat_level

Binfo

CProcess started

Dwarning

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong log level or method names.

Checking for a message not logged.

Use caplog.at_level to set capture level, logger.info to log an info message, and check the message text in caplog.text.

Practice

1. What is the purpose of the caplog fixture in pytest when testing log messages?

easy

A. To capture log messages generated during test execution

B. To mock external API calls

C. To measure test execution time

D. To generate random test data

Solution

1. Step 1: Understand the role of caplog

   The caplog fixture is designed to capture log messages during pytest test runs.

2. Step 2: Identify correct usage context

   It helps verify that expected log messages are produced, which is essential for testing logging behavior.

3. Final Answer:

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

4. Quick Check:

   caplog captures logs [OK]

Hint: Remember: caplog captures logs during tests [OK]

Common Mistakes:

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

2. Which of the following is the correct way to set the log level to capture WARNING messages but not INFO messages using caplog in pytest?

easy

A. caplog.set_level(logging.INFO)

B. caplog.set_level(logging.ERROR)

C. caplog.set_level(logging.DEBUG)

D. caplog.set_level(logging.WARNING)

Solution

1. Step 1: Understand log levels

   To capture WARNING messages but not INFO, the log level must be set to WARNING.

2. Step 2: Identify correct method call

   Using caplog.set_level(logging.WARNING) sets the capture level to WARNING, capturing WARNING and above.

3. Final Answer:

   caplog.set_level(logging.WARNING) -> Option D

4. Quick Check:

   Set level to WARNING to capture warnings [OK]

Hint: Set caplog level to desired severity (e.g., WARNING) [OK]

Common Mistakes:

• Setting level too high to capture lower severity logs
• Using incorrect logging level constants
• Not calling set_level at all

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

import logging

def test_log_message(caplog):
    with caplog.at_level(logging.ERROR):
        logging.error('Error occurred')
    assert 'Error occurred' in caplog.text

medium

A. Test passes because the error message is captured

B. Test fails because caplog.text is empty

C. Test fails due to syntax error

D. Test passes but assertion is incorrect

Solution

1. Step 1: Analyze log capture level

   The test sets caplog to capture ERROR level logs, and an error message is logged.

2. Step 2: Check assertion logic

   The assertion checks if the logged message is in caplog.text, which contains all captured logs as text.

3. Final Answer:

   Test passes because the error message is captured -> Option A

4. Quick Check:

   Logged ERROR message found in caplog.text [OK]

Hint: Check caplog.text contains your logged message [OK]

Common Mistakes:

• Assuming caplog.text is empty without setting level
• Confusing caplog.records with caplog.text
• Forgetting to set log level

4. Identify the error in the following pytest test code that uses caplog to assert a log message:

import logging

def test_info_log(caplog):
    logging.info('Info issued')
    assert 'Info issued' in caplog.text

medium

A. Logging function used is wrong

B. Incorrect assertion syntax

C. Missing setting log level to capture INFO messages

D. caplog fixture is not imported

Solution

1. Step 1: Check log level setting

   The test logs an INFO but does not set caplog to capture INFO level logs, so no logs are captured.

2. Step 2: Understand impact on assertion

   Because no logs are captured, caplog.text is empty and the assertion fails.

3. Final Answer:

   Missing setting log level to capture INFO messages -> Option C

4. Quick Check:

   Set caplog level to INFO before logging [OK]

Hint: Always set caplog level before logging messages [OK]

Common Mistakes:

• Not using caplog.at_level or caplog.set_level
• Assuming logs are captured by default
• Incorrectly placing assertion before logging

5. You want to test that your function logs an INFO message containing the word 'success'. Which pytest caplog assertion correctly verifies this?

hard

A. assert caplog.records.count('success') == 1

B. assert any('success' in record.message for record in caplog.records if record.levelname == 'INFO')

C. assert caplog.text == 'success'

D. assert 'success' in caplog.records[0]

Solution

1. Step 1: Understand caplog.records structure

   caplog.records is a list of log record objects with attributes like message and levelname.

2. Step 2: Choose correct assertion logic

   assert any('success' in record.message for record in caplog.records if record.levelname == 'INFO') checks if any INFO level record contains 'success' in its message, which correctly verifies the log content.

3. Final Answer:

   assert any('success' in record.message for record in caplog.records if record.levelname == 'INFO') -> Option B

4. Quick Check:

   Use caplog.records with message and levelname for assertions [OK]

Hint: Use caplog.records with message and levelname for checks [OK]

Common Mistakes:

• Using count on records list incorrectly
• Comparing caplog.text directly to a string
• Accessing caplog.records elements as strings