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.)

Solution 1

redirect stderr, e.g.:

python my_unit_test_launcher.py 2> log.txt

Solution 2

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)

Comments

[tadasajon]

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]

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.

[Seng Cheong]

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

[Alex Jansen]

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