How can I redirect the output of unittest? Obvious solution doesn't work

Question

Here is my code:

import unittest import sys import os class DemoTest(unittest.TestCase): def test_one(self): print "test one" self.assertTrue(True) def test_two(self): print "test two" self.assertTrue(False) if __name__ == '__main__': dirpath = os.path.dirname(os.path.abspath(__file__)) sys.stdout = open(dirpath+'/test_logs/demo_test.stdout.log', 'w') sys.stderr = open(dirpath+'/test_logs/demo_test.stderr.log', 'w') test_program = unittest.main(verbosity=0, exit=False)

When I run this, the contents of demo_test.stdout.log is only:

test one test two

on the screen I still see the output from unittest:

====================================================================== FAIL: test_two (__main__.DemoTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "demotest.py", line 12, in test_two self.assertTrue(False) AssertionError: False is not true ---------------------------------------------------------------------- Ran 2 tests in 0.000s FAILED (failures=1)

I want there to be no output on the screen and everything to be logged. (I am running the test as a cron job, so any output to stdout or stderr causes an email to be sent, so I want to be able to specify exactly when this happens, which means I need to be able to control unittest in this regard.)

Even assigning sys.__stdout__ and sys.__stderr__ fails here - I think it's impossible to redirect the output from within python itself. — Eric
– Eric, Commented Jan 9, 2013 at 21:04

Lesmana · Accepted Answer · 2016-02-16 21:39:56Z

14

redirect stderr, e.g.:

python my_unit_test_launcher.py 2> log.txt

edited Feb 16, 2016 at 21:39

Lesmana

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answered Jan 9, 2013 at 20:47

Zaur Nasibov

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3 Comments

tadasajon Over a year ago

okay, this seems to work. I'm still not sure why stderr isn't getting redirected anyway, since I explicitly set it to be redirected in my program.

Silas Ray Over a year ago

Because unittest runs your test code in a sandbox that wraps std streams. You are redirecting the output of your test code, but unittest doesn't care, because unittest normally just captures your output as basically that of a child process then regurgitates it to the context that called it. The output you are seeing, from unittest itself, is completely independent of what you do in the test code.

Alex Jansen Over a year ago

output="$(python -u some_tests.py 2>&1)" && echo "$output" # I'm trying this and it still doesn't display anything.

spoorcc · Accepted Answer · 2014-03-28 10:28:52Z

To solve it within your testcode, you could also do the following:

import sys import unittest class DemoTest(unittest.TestCase): def test_one(self): print "test one" self.assertTrue(True) def test_two(self): print "test two" self.assertTrue(False) if __name__ == "__main__": demo_test = unittest.TestLoader().loadTestsFromTestCase(DemoTest) unittest.TextTestRunner(stream=sys.stdout).run(demo_test)

TextTestRunner(stream=sys.stdout) is just what I was missing. Thanks!

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