pytest-logger

1.1.1 · active · verified Thu Apr 16

pytest-logger is a pytest plugin that configures handlers for loggers from Python's standard `logging` module. It allows directing logs to the terminal or files in a configurable manner. The current version is 1.1.1, released on March 10, 2024, indicating active maintenance and an irregular release cadence.

Common errors

```
Logs are not showing up in the console during test execution.
```
cause Pytest captures stdout/stderr by default, preventing real-time log display.

fix Run pytest with the `-s` flag (e.g., `pytest -s`) or `--capture=no`.
```
DEBUG or INFO level messages are not appearing in console/files, even after using `logging.getLogger()`.
```
cause The default root logger level might be too high (e.g., WARNING), or the `stdout_level`/`file_level` for the specific logger was not set to a sufficiently low level (e.g., 'debug' or 'info') in `pytest_logger_config`.

fix In your `conftest.py`, ensure `logger_config.add_loggers()` sets `stdout_level='debug'` and/or `file_level='debug'` for the relevant logger names. Also, check that you are running with `--log-cli-level=debug` or similar if expecting console output.
```
Log files are either not created or are empty in the specified log directory.
```
cause File logging is not explicitly enabled or configured for the loggers, or the `pytest_logger_logdirlink` hook is not correctly implemented/pointing to a writable location.

fix Ensure that `logger_config.add_loggers()` specifies a `file_level` (e.g., `file_level='debug'`). Verify that the `pytest_logger_logdirlink` hook in `conftest.py` returns a valid, writable path, and that a 'logs' directory exists or can be created relative to your tests.

Warnings

gotcha To see logs printed to the terminal in real-time during test execution, you must disable output capturing by passing the `-s` or `--capture=no` switch to pytest. Otherwise, logs will be captured and only shown upon test failure.
Fix: Run pytest with `pytest -s` or `pytest --capture=no`.
gotcha By default, Python's root logger (and its children) has a `WARNING` level threshold. If you configure any logger via `pytest-logger`, the root logger's level is set to `NOTSET` to allow all logs through. Be mindful of this default if you expect `DEBUG` or `INFO` messages from unconfigured loggers and they don't appear. Explicitly set `stdout_level` and `file_level` for desired loggers.
Fix: Explicitly set `stdout_level` and `file_level` in `logger_config.add_loggers()` for all desired loggers. Consider adding a `NullHandler` to unconfigured loggers if you encounter 'no handlers' warnings.
gotcha When using `pytest-xdist` for parallel test execution, stdout output from `pytest-logger` is not printed to the terminal. However, log file output will work as expected in single-process mode.
Fix: If real-time terminal feedback is critical, avoid `pytest-xdist` or rely on file logging for detailed analysis during parallel runs.

Install

pip install pytest-logger Install latest version

Imports

pytest_logger_config
```
# Defined in conftest.py
def pytest_logger_config(logger_config):
```
pytest-logger primarily operates through pytest hooks defined in conftest.py, rather than direct imports into test files. The main configuration entry point is the `pytest_logger_config` hook.
logging
```
import logging
```
Standard Python logging module used within tests, configured by pytest-logger.

Quickstart

To quickly get started, define `pytest_logger_config` and `pytest_logger_logdirlink` hooks in your `conftest.py` to set up loggers and a directory for log files. Then, use standard Python's `logging` module within your test files. Run pytest with `-s` to see real-time console output, and specify which loggers to display with `--loggers` and their console level with `--log-cli-level`.

# content of conftest.py
import os
import logging

def pytest_logger_config(logger_config):
    logger_config.add_loggers(['foo', 'bar'], stdout_level='info', file_level='debug')
    logger_config.set_log_option_default('foo,bar')

def pytest_logger_logdirlink(config):
    return os.path.join(os.path.dirname(__file__), 'logs')

# content of test_example.py
import logging

foo_logger = logging.getLogger('foo')
bar_logger = logging.getLogger('bar')
baz_logger = logging.getLogger('baz')

def test_logging_output():
    foo_logger.info('This is an INFO message from foo')
    bar_logger.debug('This is a DEBUG message from bar, only in file')
    baz_logger.warning('This is a WARNING from baz, not configured by default')
    assert True

# To run: pytest -s -v --log-cli-level=info --loggers=foo,bar test_example.py
# This will output foo INFO messages to console and foo (INFO) and bar (DEBUG) to files in the 'logs' directory.

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