Py.test Logging Messages And Test Results/assertions Into A Single File

I am starting to work with py.test at the moment for a new project. We are provisioning Linux servers and I need to write a script to check the setup and configuration of these ser

Solution 1:

pytest's job is to capture output and present it to the operator. So, rather than trying to get pytest to do the logging the way you want it, you can build the logging into your tests.

Python's assert command just takes a truth value, and a message. So, instead of using a bare assert in your tests, you can write a small function that does the logging if the value is false (which is the same condition that triggers the assert to fail), then calls the assert, so that you get the logging you want, plus the assert-driven behavior that creates the console output.

Here's a small test file using such a function:

# test_foo.py
import logging

def logAssert(test,msg):
    if not test:
        logging.error(msg)
        assert test,msg

def test_foo():
    logging.info("testing foo")
    logAssert( 'foo' == 'foo', "foo is not foo")

def test_foobar():
    logging.info("testing foobar")
    logAssert( 'foobar' == 'foo', "foobar is not foo")

Here's the test runner, very similar to yours:

# runtests.pyimport logging
import pytest

logging.basicConfig(filename='config_check.log', level=logging.INFO)
logging.info('start')
pytest.main()
logging.info('done')

Here's the output:

# python runtests.py
==== test session starts ========================
platform linux2 -- Python 2.6.6 -- py-1.4.22 -- pytest-2.6.0
collected 2 items

test_foo.py .F

========== FAILURES ============================
________ test_foobar __________________________

    deftest_foobar():
        logging.info("testing foobar")
>       logAssert( 'foobar' == 'foo', "foobar is not foo")

test_foo.py:14:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

test = False, msg = 'foobar is not foo'deflogAssert(test,msg):
        ifnot test:
            logging.error(msg)
>           assert test,msg
E           AssertionError: foobar isnot foo

test_foo.py:6: AssertionError    ==== 1 failed, 1 passed in0.02 seconds =======

And here's the log that gets written:

# cat config_check.log INFO:root:startINFO:root:testing fooINFO:root:testing foobarERROR:root:foobar is not fooINFO:root:done

Solution 2:

Since version 3.3, pytest supports live logging to terminal and file. Example test module:

import logging
import os


def test_taintedKernel():
    logging.info('checking for tainted kernel')
    output = os.system('cat /proc/sys/kernel/tainted')
    assertoutput == 0, 'tainted kernel found'

Configure of logging to file can be done in pytest.ini:

[pytest]log_file = my.log
log_file_level = DEBUG
log_file_format = %(asctime)s [%(levelname)8s] %(message)s (%(filename)s:%(lineno)s)
log_file_date_format=%Y-%m-%d %H:%M:%S

Running the test yields as usual:

$ pytest
======================================================= test session starts ========================================================
...
collected 1 item                                                                                                                   

test_spam.py .                                                                                                               [100%]

===================================================== 1 passed in 0.01 seconds =====================================================

Now check the written log file:

$ cat my.log
2019-07-12 23:51:41 [    INFO] checking for tainted kernel (test_spam.py:6)

For more examples of emitting live logs to both terminal and log file, check out my answer to Logging within py.test tests .

Reference: Live Logs section in pytest docs.