[Python-Dev] Tests failing on Windows with TESTFN

Nick Coghlan ncoghlan at gmail.com
Mon Jul 30 11:41:59 EDT 2018

On 29 July 2018 at 03:20, Tim Golden <mail at timgolden.me.uk> wrote:
> I think that was my starting point: rather than develop increasingly
> involved and still somewhat brittle mechanisms, why not do what you'd
> naturally do with a new test and use tempfile? I was expecting someone to
> come forward to highlight some particular reason why the TESTFN approach is
> superior, but apart from a reference to the possibly cost of creating a new
> temporary file per test, no-one really has.

For higher level modules, "just use tempfile to create a new temporary
directory, then unlink it at the end" is typically going to be a good
answer (modulo the current cleanup issues that Jeremy is reporting,
but ideally those will be fixed rather than avoided, either by
improving the way the module is being used, or fixing any underlying

For lower level modules though, adding a test suite dependency on
tempfile introduces a non-trivial chance of adding an operational
dependency from a module's test suite back to the module itself. When
that happens, module regressions may show up as secondary failures in
tempfile that then need to be debugged, rather than as specific unit
test failures that point you towards exactly what you broke.


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

More information about the Python-Dev mailing list