repro_test_failure.md

Instructions

These are steps for attempting to reproduce this test failure.

Get the repository

If you don't have CPython cloned locally

If you don't already have a local CPython clone, go to wherever you clone repositories and execute:

git clone git@github.com:python/cpython.git
cd cpython

Then proceed to the next step

From the CPython directory

Once cloned, you need to add my fork as a remote and fetch my branches

git remote add pganssle git@github.com:pganssle/cpython.git
git fetch pganssle

Check out the commit that will fail

git checkout failing_fix_surrogate_strftime

If this doesn't work, you can check it out by commit id:

git checkout b643da871a

Build CPython

Assuming you have the build dependencies installed, you can do this to build CPython:

./configure
make

For more details on building CPython, see the Python dev guide.

Execute the tests

To save yourself some time, just execute the test_datetime tests:

./python -m test test_datetime

Though if you want to run the full test suite, you can with:

./python -m test

While it doesn't help directly with reproducing the failure, note that the erroneous output reported in the tests reflects a case of encoding with surrogatepass, then decoding with surrogateescape:

>>> '\ud800'.encode(errors='surrogatepass').decode(errors='surrogateescape')
'\udced\udca0\udc80'