In #153, I added test_set_include_dirs. At least on my mac, this operation leaves a file in the working directory:

private/var/folders/sx/n5gkrgfx6zd91ymxr2sr9wvw00n8zm/T/pytest-of-jaraco/pytest-32/test_set_include_dirs0/foo.o

It seems something about invoking a compiler on a file causes the path for that file to get built relative to the current directory :/