[Python-Dev] test___all__ polluting sys.modules? (original) (raw)

Gregory P. Smith greg at krypto.org
Tue Jan 1 04:30:51 CET 2013

On Sun, Dec 30, 2012 at 6:48 AM, R. David Murray <rdmurray at bitdance.com>wrote:

On Mon, 31 Dec 2012 00:38:47 +1000, Nick Coghlan <ncoghlan at gmail.com> wrote: > On Mon, Dec 31, 2012 at 12:19 AM, Eli Bendersky <eliben at gmail.com> wrote: > > On Sun, Dec 30, 2012 at 5:54 AM, Stefan Krah <stefan at bytereef.org> wrote: > >> > >> Eli Bendersky <eliben at gmail.com> wrote: > >> > Yes, this is the solution currently used in testxmletree. However, > >> > once > >> > pickling tests are added things stop working. Pickle uses import to > >> > import > >> > the module a class belongs to, bypassing all such trickery. So if > >> > test_all_ > >> > got elementtree into sys.modules, pickle's import finds it even if > >> > all the > >> > tests in testxmletree manage to ignore it for the Python version > >> > because they > >> > use importfreshmodule. > >> > >> I ran into the same problem for testdecimal. The only thing that appears > >> to work is to set sys.modules['decimal'] explicitly before calling > >> dumps()/loads(). See: > >> > >> PythonAPItests.testpickle() > >> ContextAPItests.testpickle() > > > > Yes, this seems to have done the trick. Thanks for the suggestion. > > It may be worth offering a context manager/decorator equivalent to > "importfreshmodule".

I suggested making importfreshmodule a context manager in the issue that Eli opened about test_all._ > > I'm still curious about the test-in-clean-env question though. > > As Stefan noted, the main advantage we get is that sometimes the > failure to clean up properly is in the standard lib code rather than > the tests, and with complete isolation we'd be less likely to notice > the problem. > > Once you combine that with the fact that rearchitecting regrtest to > work that way would be quite a bit of work, the motivation to make it > happen goes way down. > > However, specifically spinning out the "import the world" tests like > testpydoc and test_all to a separate process might be worth the_ > effort. Adding something to regertest (or unittest?) so that certain nominated test modules are run in a subprocess has been discussed previously, but so far no one has stepped up to implement it :) (I think this came up originally for testsite, but I don't remember for sure.)

test_subprocess and possibly a few others (things testing signal behavior, etc) already have some individual tests that do this. its pretty easy. subprocess.Popen of sys.executable typically with -E and the code either in a string via -c or else point at a second file or add an argument for main in the current file to detect. making this simpler via something in test.support might make sense if there is a common need for it.

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