Python | Logging Test Output to a File

Problem – Writing the results of running unit tests to a file instead of printed to standard output.

A very common technique for running unit tests is to include a small code fragment (as shown in the code given below) at the bottom of your testing file.

Code #1 :



filter_none

edit
close

play_arrow

link
brightness_4
code

import unittest
class MyTest(unittest.TestCase):
    ...
if __name__ == '__main__':
    unittest.main()

chevron_right


This makes the test file executable, and prints the results of running tests to standard output. To redirect this output, unwind the main() call a bit and write own main() function as shown in the code given below :

Code #2 :

filter_none

edit
close

play_arrow

link
brightness_4
code

import sys
  
def main(out = sys.stderr, verbosity = 2):
    loader = unittest.TestLoader()
  
    suite = loader.loadTestsFromModule(sys.modules[__name__])
    unittest.TextTestRunner(out, verbosity = verbosity).run(suite)
      
if __name__ == '__main__':
    with open('testing.out', 'w') as f:
        main(f)

chevron_right


How it works :

  • The interesting thing about the code is not so much the task of getting test results redirected to a file, but the fact that doing so exposes some notable inner workings of the unittest module.
  • At a basic level, the unittest module works by first assembling a test suite.
  • This test suite consists of the different testing methods you defined. Once the suite has been assembled, the tests it contains are executed.
  • These two parts of unit testing are separate from each other. The unittest.TestLoader instance created in the solution is used to assemble a test suite.
  • The loadTestsFromModule() is one of several methods it defines to gather tests. In this case, it scans a module for TestCase classes and extracts test methods from them.
  • The loadTestsFromTestCase() method (not shown) can be used to pull test methods from an individual class that inherits from TestCase.
  • The TextTestRunner class is an example of a test runner class. The main purpose of this class is to execute the tests contained in a test suite. This class is the same test runner that sits behind the unittest.main() function.


My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.




Article Tags :

Be the First to upvote.


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.