Test conditions under which st_mtime of a directory changes

test_dir_mtime.py

# -*- coding: utf-8 -*-
'''
This module tests the circumstances under which a directory's st_mtime changes.
Precision is determined by the current file system. On Windows with NTFS the
tests will pass when the time between changes is as low as 0.01 seconds. If
you set the INTERVAL to 0 you'll discover how inconsistent the tests become.
On Unix based systems with other file systems the time between changes must
increase in order for the tests to pass, in the worst case up to 2 seconds.

Runs with a default SLEEP_INTERVAL of 0.1 seconds. You can pass a different
SLEEP_INTERVAL like so:

    python -m dir_mtime 2.0

'''
from __future__ import absolute_import, division, print_function
import os
import shutil
import time
import unittest
from datetime import datetime
from contextlib import contextmanager


SLEEP_INTERVAL = 0.1


def time_since_modified(path):
    return (
        datetime.now()
      - datetime.fromtimestamp(os.path.getmtime(path))
    ).total_seconds()


def mtime(*paths):
    return os.path.getmtime(os.path.join(*paths))


def link_dir(*paths):
    try:
        os.makedirs(os.path.join(*paths))
    except:
        pass


def link(*paths):
    file = os.path.join(*paths)
    dir = os.path.dirname(file)
    if not os.path.exists(dir):
        make_dir(dir)
    touch(file)


def unlink(*paths):
    path = os.path.join(*paths)
    if os.path.isdir(path):
        shutil.rmtree(path)
    else:
        os.remove(path)


def touch(*paths):
    file = os.path.join(*paths)
    with open(file, 'a'):
        os.utime(file, None)


@contextmanager
def assert_mtime_changed(path, value, sleep_interval):

    mt = mtime(path)
    if value:
        msg = path + ' mtime has not changed'
    else:
        msg = path + ' mtime changed'

    try:
        if sleep_interval:
            time.sleep(sleep_interval)
        yield
    finally:
        assert (mt != mtime(path)) == value, msg


class TestMTime(unittest.TestCase):

    def test_subdir_created(self):
        '''mtime changes when subdir created'''

        link_dir('tmp')

        with assert_mtime_changed('tmp', True, SLEEP_INTERVAL):
            link_dir('tmp', 'subdir')

        unlink('tmp')


    def test_subdir_deleted(self):
        '''mtime changes when subdir deleted'''

        link_dir('tmp')
        link_dir('tmp', 'subdir')

        with assert_mtime_changed('tmp', True, SLEEP_INTERVAL):
            unlink('tmp', 'subdir')

        unlink('tmp')


    def test_subfile_created(self):
        '''mtime changes when subfile created'''

        link_dir('tmp')

        with assert_mtime_changed('tmp', True, SLEEP_INTERVAL):
            link('tmp', 'file')

        unlink('tmp')


    def test_subfile_changed(self):
        '''mtime changes when subfile changed'''

        link_dir('tmp')
        link('tmp', 'file')

        with assert_mtime_changed('tmp', False, SLEEP_INTERVAL):
            touch('tmp', 'file')

        unlink('tmp')



    def test_subfile_deleted(self):
        '''mtime changes when subfile deleted'''

        link_dir('tmp')
        link('tmp', 'file')

        with assert_mtime_changed('tmp', True, SLEEP_INTERVAL):
            unlink('tmp', 'file')

        unlink('tmp')


if __name__ == '__main__':
    import sys
    args = sys.argv[1:]
    if len(args) == 1:
        SLEEP_INTERVAL = float(args[0])
    
    print('Running tests with SLEEP_INTERVAL:', SLEEP_INTERVAL, 'seconds')
    
    loader = unittest.TestLoader()
    suite = loader.loadTestsFromTestCase(TestMTime)
    unittest.TextTestRunner(verbosity=2).run(suite)