Question: How to remove duplication of loguru logger patching in pytest (hashtag1153)

[vikramsubramanian]

I am testing a function which calls loguru.logger.add("file.log") at the start. This causes issues during pytest execution. The file is written to a temp dir and thus is being used by another process (good ol' Windows) when clean-up happens.

PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'path/to/tmp_dir/file.log'

One solution is to patch loguru.logger.add on each test. But this results in much repeated (boilerplate?) code. For many tests, I don't need to refer to logger.add, just need patch it so the test runs.

def test_one(mock_logger_add):
    ...
    hashtag Useful to check, but don't want to call this in EVERY test
    mock_logger_add.assert_called_once()

def test_two(mock_logger_add):
    ...
    hashtag No need to check mock_logger_add, just want my code to run

How can I reduce this duplication?

Things I've tried:

• Adding an autouse=True fixture to conftest.py or in the test file/class

e.g.

def patch_logger_add(monkeypatch):
    monkeypatch.setattr("loguru.logger.add", lambda *args, **kwargs: None)
    hashtag or
    hashtag monkeypatch.setattr("loguru.logger.add", MagicMock())

or

def no_logger_add(monkeypatch):
    monkeypatch.delattr("loguru.logger.add")

These don't work. Perhaps because, in order for loguru to work with pytest, we have to [redefine caplog]( and that involves calling logger.add.

This works but only when I do not pass caplog to my tests.

def patch_logger():
    with patch("loguru.logger.add"):
        yield

Note: I do not want to turn loguru off completely because I check the logs for errors in my tests.

I posted this also on [SO]( but didn't get much response so wondered if I'd get better results here. )

[mayil-ai[bot]]

Some past issues to consider:

• Pytest's caplog fixture with multiprocessing (hashtag573) | Discusses using pytest's caplog with loguru, similar to current issue's logger handling.

To address the issue of avoiding repetitive patching of loguru.logger.add in each pytest test and preventing PermissionError due to file access conflicts on Windows, follow these actionable steps:

1. Create an autouse=True Fixture in conftest.py: This fixture will automatically patch loguru.logger.add for all tests, eliminating the need to patch it in each individual test.

   import pytest
   from unittest.mock import patch
   
   @pytest.fixture(autouse=True)
   def patch_logger_add():
      with patch("loguru.logger.add", lambda *args, **kwargs: None):
          yield

2. Ensure Compatibility with caplog: To capture logs correctly using caplog, ensure that enqueue=True is used when adding the log handler.

   import pytest
   from loguru import logger
   
   @pytest.fixture
   def caplog(_caplog):
      handler_id = logger.add(_caplog.handler, format="{message}", enqueue=True)
      yield _caplog
      logger.remove(handler_id)

3. Use the Fixtures in Your Tests: With the patch_logger_add fixture set to autouse=True, it will automatically apply to all tests. You can now write your tests without worrying about patching loguru.logger.add in each one.

   def test_one(caplog):
      # Your test code here
      pass
   
   def test_two(caplog):
      # Your test code here
      pass

By following these steps, you can reduce the duplication of patching loguru.logger.add in your tests and ensure smooth pytest execution without file access conflicts.

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