remove generated dataset folders after download tests

[pmeier]

While the actual download and extraction logic is mocked, some datasets still create an extra directory in the root directory:

vision/torchvision/datasets/mnist.py

Lines 140 to 141 in 5905de0

	os.makedirs(self.raw_folder, exist_ok=True)
	os.makedirs(self.processed_folder, exist_ok=True)

vision/torchvision/datasets/caltech.py

Line 44 in 5905de0

os.makedirs(self.root, exist_ok=True)

With this, all tests use a temporary directory instead of the current directory as root for the datasets. This temporary directory is simply removed after all tests are run.

Another option would be to mock the function that creates the extra directory (here os.makedirs). While not complicated, we would than need to manually check during code review that either

• only the already mocked functions are used to create directories, or
• the new function is added to the list of mocked functions.

[codecov]

Codecov Report

Merging #3376 (5669c78) into master (5905de0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3376   +/-   ##
=======================================
  Coverage   74.80%   74.80%           
=======================================
  Files         105      105           
  Lines        9716     9716           
  Branches     1561     1561           
=======================================
  Hits         7268     7268           
  Misses       1961     1961           
  Partials      487      487           

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[datumbox]

Looks good, I just left one comment. If you could provide a few more information so that we have history of how this works that would be awesome.

[datumbox]

I understand that you are using pytest specific functionalities here but could you elaborate on when this is triggered?

[pmeier]

The autouse=True flag tells pytest to trigger this automatically even if it is not explicitly used. The scope="module" tells pytest to run this once per module. In general, everything before the yield is the setup whereas everything after it is the teardown.

Here, pytest triggers this fixture the first time any test in this module is run and finishes it when the last test is run.