PyDev unittesting: How to capture text logged to a logging.Logger in “Captured Output”

Question

I am using PyDev for development and unit-testing of my Python application. As for unit-testing, everything works great except the fact that no content is logged to the logg

Answer 1

The issue is that the unittest runner replaces sys.stdout/sys.stderr before the testing starts, and the StreamHandler is still writing to the original sys.stdout.

If you assign the 'current' sys.stdout to the handler, it should work (see the code below).

import sys
import unittest
import logging

logger = logging.getLogger()
logger.level = logging.DEBUG
stream_handler = logging.StreamHandler(sys.stdout)
logger.addHandler(stream_handler)

class TestCase(unittest.TestCase):
    def testSimpleMsg(self):
        stream_handler.stream = sys.stdout
        print("AA")
        logging.getLogger().info("BB")

Although, a better approach would be adding/removing the handler during the test:

import sys
import unittest
import logging

logger = logging.getLogger()
logger.level = logging.DEBUG

class TestCase(unittest.TestCase):
    def testSimpleMsg(self):
        stream_handler = logging.StreamHandler(sys.stdout)
        logger.addHandler(stream_handler)
        try:
            print("AA")
            logging.getLogger().info("BB")
        finally:
            logger.removeHandler(stream_handler)