socialmedian: Peter Bengtsson: Mocking os.stat in Python

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Peter Bengtsson: Mocking os.stat in Python

Submitted by Jgmize from Google Reader

Nov 08, 2009

Summary

I have some code that checks that a file is treated differently if some time has passed. In other words, it reacts if the modification time is more than it was before. The code uses os.stat(filename)[stat.ST_MTIME] to do this. The challenge was to mock os.stat so that I can pretend some time has passed without having to wait. Here was my first solution which made running many tests sloooow:

def test_file_changed(self):

     filename = 'foo.txt'

     expect_timestamp = int(time.time())

     ...run the unit test with 'expect_timestamp'...

     time.sleep(1)

     expect_timestamp += 1

     ...run the unit test with 'expect_timestamp'...

So, here's how I mock os.stat to avoid having to do the time.sleep(1) in the test:

def test_file_changed(self):

     filename = 'foo.txt'

     expect_timestamp = int(time.time())

     ...run the unit test with 'expect_timestamp'...

     import os

     from posix import stat_result

     def fake_stat(arg):

         if arg == filename:

             faked = list(orig_os_stat(arg))

             faked[stat.ST_MTIME] = faked[stat.ST_MTIME] + 1

...Read the full article

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