ability to run code as non-root

[FelixSchwarz]

Some CI services (e.g. shippable) run code under the "root" user. Since commit c16a508 (PR #455, pyfakefs 3.5.4) pyfakefs uses the value from os.getuid() to emulate root permissions.

Some of my tests broke with that version as I tried to test for non-accessible files (using os.chmod(..., 0). Of course root can access all files.

Describe the solution you'd like
Ideally I'd like to tell pyfakefs to emulate a non-root user even though the Unix user might be "root". The setting should only be active for a given test (maybe bound to the "Patcher()" instance?).

I use the "Patcher" manually anyway so adding a parameter to the constructor or the .setUp() call (e.g. root_user=False) would be pretty easy.

    patcher = Patcher()
    patcher.setUp()
    self.addCleanup(patcher.tearDown)

Describe alternatives you've considered
I could do the same as some pyfakefs tests (e.g. FakeOsModuleTest) which means calling set_uid(1) manually. However that means additional boilerplate code (remembering the old value, using tearDown() to restore it, dealing with Windows).

class FakeOsModuleTest(FakeOsModuleTestBase):
    def setUp(self):
        super(FakeOsModuleTest, self).setUp()
        # ...
        set_uid(1)

[mrbean-bremen]

This makes sense. I'm a bit reluctant to add another argument to Patcher, but this is probably the best way. I will sleep on the matter, and if nothing else comes to mind, will add this.

[mrbean-bremen]

Ok, I added something - please check if that is what you need!

[FelixSchwarz]

Yes, that code works fine :-)