How to test if exception was caught while running a django test

Question

Suppose this is my code:

def fun():
   try:
      raise Exception("An exception")
   except Exception as e:
      logger.debug(f'{e}')

Now how can I write a test case which checks if that particular exception was caught? I could have tested by reading sys.stderr, but I'm using logger.debug. I'm using django TestCase

Answer 1

You can use assertLogs, but i suggest to add a "prefix" to your log, this way you can test that the right message was logged.

Example:

logger = logging.getLogger('foo')

def fun():
   try:
      raise Exception("An exception")
   except Exception as e:
      logger.debug(f'[error-x]: {e}')

Your test:

with self.assertLogs('foo', level=logging.DEBUG) as cm:
    call_your_method()
self.assertEqual(cm.output, ["DEBUG:foo:[error-x]: An exception"])

If you have more log messages with your exception message you can do:

self.assertIn("DEBUG:foo:[error-x]: An exception", cm.output)

You can check the full example here