trial.test.test_loader.FileTest.test_directory modifies the twisted installation

[radix]

This makes it fail if you're running the tests on a system-installed Twisted.

[TimAllen]

Test_directory wants to test that runner.filenameToModule(path) will work identically whether or not path has a trailing slash. It seems that for this to work, path must be an importable Python package or a sub-package of an importable package. The test reasonably assumes it's currently in an importable package, so constructs a temporary package along-side to use for its tests, which causes problems.

Potential solutions include:

• Create a dummy directory in $PWD (which should be the writable _trial_temp directory), mess with sys.path to make it importable.
• Test with a path derived from __file__ which we already know is an importable package, instead of trying to construct a new package at runtime.

I'm not sure which would be better, but both seem like they should be fairly easy.

[radix]

I recommend the first solution. I think we use it elsewhere in similar situations in the Twisted test suite.

[spiv]

FWIW, the first solution sounds good to me too.