# -*- test-case-name: twisted.test.test_util -*-
# Copyright (c) 2001-2010 Twisted Matrix Laboratories.
# See LICENSE for details.

import os.path, sys
import shutil, errno
try:
    import pwd, grp
except ImportError:
    pwd = grp = None

from twisted.trial import unittest

from twisted.python import util
from twisted.internet import reactor
from twisted.internet.interfaces import IReactorProcess
from twisted.internet.protocol import ProcessProtocol
from twisted.internet.defer import Deferred
from twisted.internet.error import ProcessDone

from twisted.test.test_process import MockOS



class UtilTestCase(unittest.TestCase):

    def testUniq(self):
        l = ["a", 1, "ab", "a", 3, 4, 1, 2, 2, 4, 6]
        self.assertEquals(util.uniquify(l), ["a", 1, "ab", 3, 4, 2, 6])

    def testRaises(self):
        self.failUnless(util.raises(ZeroDivisionError, divmod, 1, 0))
        self.failIf(util.raises(ZeroDivisionError, divmod, 0, 1))

        try:
            util.raises(TypeError, divmod, 1, 0)
        except ZeroDivisionError:
            pass
        else:
            raise unittest.FailTest, "util.raises didn't raise when it should have"

    def testUninterruptably(self):
        def f(a, b):
            self.calls += 1
            exc = self.exceptions.pop()
            if exc is not None:
                raise exc(errno.EINTR, "Interrupted system call!")
            return a + b

        self.exceptions = [None]
        self.calls = 0
        self.assertEquals(util.untilConcludes(f, 1, 2), 3)
        self.assertEquals(self.calls, 1)

        self.exceptions = [None, OSError, IOError]
        self.calls = 0
        self.assertEquals(util.untilConcludes(f, 2, 3), 5)
        self.assertEquals(self.calls, 3)

    def testNameToLabel(self):
        """
        Test the various kinds of inputs L{nameToLabel} supports.
        """
        nameData = [
            ('f', 'F'),
            ('fo', 'Fo'),
            ('foo', 'Foo'),
            ('fooBar', 'Foo Bar'),
            ('fooBarBaz', 'Foo Bar Baz'),
            ]
        for inp, out in nameData:
            got = util.nameToLabel(inp)
            self.assertEquals(
                got, out,
                "nameToLabel(%r) == %r != %r" % (inp, got, out))


    def test_uidFromNumericString(self):
        """
        When L{uidFromString} is called with a base-ten string representation
        of an integer, it returns the integer.
        """
        self.assertEqual(util.uidFromString("100"), 100)


    def test_uidFromUsernameString(self):
        """
        When L{uidFromString} is called with a base-ten string representation
        of an integer, it returns the integer.
        """
        pwent = pwd.getpwuid(os.getuid())
        self.assertEqual(util.uidFromString(pwent.pw_name), pwent.pw_uid)
    if pwd is None:
        test_uidFromUsernameString.skip = (
            "Username/UID conversion requires the pwd module.")


    def test_gidFromNumericString(self):
        """
        When L{gidFromString} is called with a base-ten string representation
        of an integer, it returns the integer.
        """
        self.assertEqual(util.gidFromString("100"), 100)


    def test_gidFromGroupnameString(self):
        """
        When L{gidFromString} is called with a base-ten string representation
        of an integer, it returns the integer.
        """
        grent = grp.getgrgid(os.getgid())
        self.assertEqual(util.gidFromString(grent.gr_name), grent.gr_gid)
    if grp is None:
        test_gidFromGroupnameString.skip = (
            "Group Name/GID conversion requires the grp module.")


    def test_moduleMovedForSplitDeprecation(self):
        """
        Calling L{moduleMovedForSplit} results in a deprecation warning.
        """
        util.moduleMovedForSplit("foo", "bar", "baz", "quux", "corge", {})
        warnings = self.flushWarnings(
            offendingFunctions=[self.test_moduleMovedForSplitDeprecation])
        self.assertEquals(
            warnings[0]['message'],
            "moduleMovedForSplit is deprecated since Twisted 9.0.")
        self.assertEquals(warnings[0]['category'], DeprecationWarning)
        self.assertEquals(len(warnings), 1)



class TestMergeFunctionMetadata(unittest.TestCase):
    """
    Tests for L{mergeFunctionMetadata}.
    """

    def test_mergedFunctionBehavesLikeMergeTarget(self):
        """
        After merging C{foo}'s data into C{bar}, the returned function behaves
        as if it is C{bar}.
        """
        foo_object = object()
        bar_object = object()

        def foo():
            return foo_object

        def bar(x, y, (a, b), c=10, *d, **e):
            return bar_object

        baz = util.mergeFunctionMetadata(foo, bar)
        self.assertIdentical(baz(1, 2, (3, 4), quux=10), bar_object)


    def test_moduleIsMerged(self):
        """
        Merging C{foo} into C{bar} returns a function with C{foo}'s
        C{__module__}.
        """
        def foo():
            pass

        def bar():
            pass
        bar.__module__ = 'somewhere.else'

        baz = util.mergeFunctionMetadata(foo, bar)
        self.assertEqual(baz.__module__, foo.__module__)


    def test_docstringIsMerged(self):
        """
        Merging C{foo} into C{bar} returns a function with C{foo}'s docstring.
        """

        def foo():
            """
            This is foo.
            """

        def bar():
            """
            This is bar.
            """

        baz = util.mergeFunctionMetadata(foo, bar)
        self.assertEqual(baz.__doc__, foo.__doc__)


    def test_nameIsMerged(self):
        """
        Merging C{foo} into C{bar} returns a function with C{foo}'s name.
        """

        def foo():
            pass

        def bar():
            pass

        baz = util.mergeFunctionMetadata(foo, bar)
        self.assertEqual(baz.__name__, foo.__name__)


    def test_instanceDictionaryIsMerged(self):
        """
        Merging C{foo} into C{bar} returns a function with C{bar}'s
        dictionary, updated by C{foo}'s.
        """

        def foo():
            pass
        foo.a = 1
        foo.b = 2

        def bar():
            pass
        bar.b = 3
        bar.c = 4

        baz = util.mergeFunctionMetadata(foo, bar)
        self.assertEqual(foo.a, baz.a)
        self.assertEqual(foo.b, baz.b)
        self.assertEqual(bar.c, baz.c)



class OrderedDictTest(unittest.TestCase):
    def testOrderedDict(self):
        d = util.OrderedDict()
        d['a'] = 'b'
        d['b'] = 'a'
        d[3] = 12
        d[1234] = 4321
        self.assertEquals(repr(d), "{'a': 'b', 'b': 'a', 3: 12, 1234: 4321}")
        self.assertEquals(d.values(), ['b', 'a', 12, 4321])
        del d[3]
        self.assertEquals(repr(d), "{'a': 'b', 'b': 'a', 1234: 4321}")
        self.assertEquals(d, {'a': 'b', 'b': 'a', 1234:4321})
        self.assertEquals(d.keys(), ['a', 'b', 1234])
        self.assertEquals(list(d.iteritems()),
                          [('a', 'b'), ('b','a'), (1234, 4321)])
        item = d.popitem()
        self.assertEquals(item, (1234, 4321))

    def testInitialization(self):
        d = util.OrderedDict({'monkey': 'ook',
                              'apple': 'red'})
        self.failUnless(d._order)

        d = util.OrderedDict(((1,1),(3,3),(2,2),(0,0)))
        self.assertEquals(repr(d), "{1: 1, 3: 3, 2: 2, 0: 0}")

class InsensitiveDictTest(unittest.TestCase):
    def testPreserve(self):
        InsensitiveDict=util.InsensitiveDict
        dct=InsensitiveDict({'Foo':'bar', 1:2, 'fnz':{1:2}}, preserve=1)
        self.assertEquals(dct['fnz'], {1:2})
        self.assertEquals(dct['foo'], 'bar')
        self.assertEquals(dct.copy(), dct)
        self.assertEquals(dct['foo'], dct.get('Foo'))
        assert 1 in dct and 'foo' in dct
        self.assertEquals(eval(repr(dct)), dct)
        keys=['Foo', 'fnz', 1]
        for x in keys:
            assert x in dct.keys()
            assert (x, dct[x]) in dct.items()
        self.assertEquals(len(keys), len(dct))
        del dct[1]
        del dct['foo']

    def testNoPreserve(self):
        InsensitiveDict=util.InsensitiveDict
        dct=InsensitiveDict({'Foo':'bar', 1:2, 'fnz':{1:2}}, preserve=0)
        keys=['foo', 'fnz', 1]
        for x in keys:
            assert x in dct.keys()
            assert (x, dct[x]) in dct.items()
        self.assertEquals(len(keys), len(dct))
        del dct[1]
        del dct['foo']




class PasswordTestingProcessProtocol(ProcessProtocol):
    """
    Write the string C{"secret\n"} to a subprocess and then collect all of
    its output and fire a Deferred with it when the process ends.
    """
    def connectionMade(self):
        self.output = []
        self.transport.write('secret\n')

    def childDataReceived(self, fd, output):
        self.output.append((fd, output))

    def processEnded(self, reason):
        self.finished.callback((reason, self.output))


class GetPasswordTest(unittest.TestCase):
    if not IReactorProcess.providedBy(reactor):
        skip = "Process support required to test getPassword"

    def test_stdin(self):
        """
        Making sure getPassword accepts a password from standard input by
        running a child process which uses getPassword to read in a string
        which it then writes it out again.  Write a string to the child
        process and then read one and make sure it is the right string.
        """
        p = PasswordTestingProcessProtocol()
        p.finished = Deferred()
        reactor.spawnProcess(
            p,
            sys.executable,
            [sys.executable,
             '-c',
             ('import sys\n'
             'from twisted.python.util import getPassword\n'
              'sys.stdout.write(getPassword())\n'
              'sys.stdout.flush()\n')],
            env={'PYTHONPATH': os.pathsep.join(sys.path)})

        def processFinished((reason, output)):
            reason.trap(ProcessDone)
            self.assertIn((1, 'secret'), output)

        return p.finished.addCallback(processFinished)



class SearchUpwardsTest(unittest.TestCase):
    def testSearchupwards(self):
        os.makedirs('searchupwards/a/b/c')
        file('searchupwards/foo.txt', 'w').close()
        file('searchupwards/a/foo.txt', 'w').close()
        file('searchupwards/a/b/c/foo.txt', 'w').close()
        os.mkdir('searchupwards/bar')
        os.mkdir('searchupwards/bam')
        os.mkdir('searchupwards/a/bar')
        os.mkdir('searchupwards/a/b/bam')
        actual=util.searchupwards('searchupwards/a/b/c',
                                  files=['foo.txt'],
                                  dirs=['bar', 'bam'])
        expected=os.path.abspath('searchupwards') + os.sep
        self.assertEqual(actual, expected)
        shutil.rmtree('searchupwards')
        actual=util.searchupwards('searchupwards/a/b/c',
                                  files=['foo.txt'],
                                  dirs=['bar', 'bam'])
        expected=None
        self.assertEqual(actual, expected)

class Foo:
    def __init__(self, x):
        self.x = x

class DSU(unittest.TestCase):
    """
    Tests for L{util.dsu}
    """
    def test_dsu(self):
        L = [Foo(x) for x in range(20, 9, -1)]
        L2 = util.dsu(L, lambda o: o.x)
        self.assertEquals(range(10, 21), [o.x for o in L2])


    def test_deprecation(self):
        self.assertWarns(DeprecationWarning,
                         ("dsu is deprecated since Twisted 10.1. "
                          "Use the built-in sorted() instead."),
                         __file__, lambda: util.dsu([], lambda: 0))



class IntervalDifferentialTestCase(unittest.TestCase):
    def testDefault(self):
        d = iter(util.IntervalDifferential([], 10))
        for i in range(100):
            self.assertEquals(d.next(), (10, None))

    def testSingle(self):
        d = iter(util.IntervalDifferential([5], 10))
        for i in range(100):
            self.assertEquals(d.next(), (5, 0))

    def testPair(self):
        d = iter(util.IntervalDifferential([5, 7], 10))
        for i in range(100):
            self.assertEquals(d.next(), (5, 0))
            self.assertEquals(d.next(), (2, 1))
            self.assertEquals(d.next(), (3, 0))
            self.assertEquals(d.next(), (4, 1))
            self.assertEquals(d.next(), (1, 0))
            self.assertEquals(d.next(), (5, 0))
            self.assertEquals(d.next(), (1, 1))
            self.assertEquals(d.next(), (4, 0))
            self.assertEquals(d.next(), (3, 1))
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (5, 0))
            self.assertEquals(d.next(), (0, 1))

    def testTriple(self):
        d = iter(util.IntervalDifferential([2, 4, 5], 10))
        for i in range(100):
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (0, 1))
            self.assertEquals(d.next(), (1, 2))
            self.assertEquals(d.next(), (1, 0))
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (0, 1))
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (0, 2))
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (0, 1))
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (1, 2))
            self.assertEquals(d.next(), (1, 0))
            self.assertEquals(d.next(), (0, 1))
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (2, 0))
            self.assertEquals(d.next(), (0, 1))
            self.assertEquals(d.next(), (0, 2))

    def testInsert(self):
        d = iter(util.IntervalDifferential([], 10))
        self.assertEquals(d.next(), (10, None))
        d.addInterval(3)
        self.assertEquals(d.next(), (3, 0))
        self.assertEquals(d.next(), (3, 0))
        d.addInterval(6)
        self.assertEquals(d.next(), (3, 0))
        self.assertEquals(d.next(), (3, 0))
        self.assertEquals(d.next(), (0, 1))
        self.assertEquals(d.next(), (3, 0))
        self.assertEquals(d.next(), (3, 0))
        self.assertEquals(d.next(), (0, 1))

    def testRemove(self):
        d = iter(util.IntervalDifferential([3, 5], 10))
        self.assertEquals(d.next(), (3, 0))
        self.assertEquals(d.next(), (2, 1))
        self.assertEquals(d.next(), (1, 0))
        d.removeInterval(3)
        self.assertEquals(d.next(), (4, 0))
        self.assertEquals(d.next(), (5, 0))
        d.removeInterval(5)
        self.assertEquals(d.next(), (10, None))
        self.assertRaises(ValueError, d.removeInterval, 10)



class Record(util.FancyEqMixin):
    """
    Trivial user of L{FancyEqMixin} used by tests.
    """
    compareAttributes = ('a', 'b')

    def __init__(self, a, b):
        self.a = a
        self.b = b



class DifferentRecord(util.FancyEqMixin):
    """
    Trivial user of L{FancyEqMixin} which is not related to L{Record}.
    """
    compareAttributes = ('a', 'b')

    def __init__(self, a, b):
        self.a = a
        self.b = b



class DerivedRecord(Record):
    """
    A class with an inheritance relationship to L{Record}.
    """



class EqualToEverything(object):
    """
    A class the instances of which consider themselves equal to everything.
    """
    def __eq__(self, other):
        return True


    def __ne__(self, other):
        return False



class EqualToNothing(object):
    """
    A class the instances of which consider themselves equal to nothing.
    """
    def __eq__(self, other):
        return False


    def __ne__(self, other):
        return True



class EqualityTests(unittest.TestCase):
    """
    Tests for L{FancyEqMixin}.
    """
    def test_identity(self):
        """
        Instances of a class which mixes in L{FancyEqMixin} but which
        defines no comparison attributes compare by identity.
        """
        class Empty(util.FancyEqMixin):
            pass

        self.assertFalse(Empty() == Empty())
        self.assertTrue(Empty() != Empty())
        empty = Empty()
        self.assertTrue(empty == empty)
        self.assertFalse(empty != empty)


    def test_equality(self):
        """
        Instances of a class which mixes in L{FancyEqMixin} should compare
        equal if all of their attributes compare equal.  They should not
        compare equal if any of their attributes do not compare equal.
        """
        self.assertTrue(Record(1, 2) == Record(1, 2))
        self.assertFalse(Record(1, 2) == Record(1, 3))
        self.assertFalse(Record(1, 2) == Record(2, 2))
        self.assertFalse(Record(1, 2) == Record(3, 4))


    def test_unequality(self):
        """
        Unequality between instances of a particular L{record} should be
        defined as the negation of equality.
        """
        self.assertFalse(Record(1, 2) != Record(1, 2))
        self.assertTrue(Record(1, 2) != Record(1, 3))
        self.assertTrue(Record(1, 2) != Record(2, 2))
        self.assertTrue(Record(1, 2) != Record(3, 4))


    def test_differentClassesEquality(self):
        """
        Instances of different classes which mix in L{FancyEqMixin} should not
        compare equal.
        """
        self.assertFalse(Record(1, 2) == DifferentRecord(1, 2))


    def test_differentClassesInequality(self):
        """
        Instances of different classes which mix in L{FancyEqMixin} should
        compare unequal.
        """
        self.assertTrue(Record(1, 2) != DifferentRecord(1, 2))


    def test_inheritedClassesEquality(self):
        """
        An instance of a class which derives from a class which mixes in
        L{FancyEqMixin} should compare equal to an instance of the base class
        if and only if all of their attributes compare equal.
        """
        self.assertTrue(Record(1, 2) == DerivedRecord(1, 2))
        self.assertFalse(Record(1, 2) == DerivedRecord(1, 3))
        self.assertFalse(Record(1, 2) == DerivedRecord(2, 2))
        self.assertFalse(Record(1, 2) == DerivedRecord(3, 4))


    def test_inheritedClassesInequality(self):
        """
        An instance of a class which derives from a class which mixes in
        L{FancyEqMixin} should compare unequal to an instance of the base
        class if any of their attributes compare unequal.
        """
        self.assertFalse(Record(1, 2) != DerivedRecord(1, 2))
        self.assertTrue(Record(1, 2) != DerivedRecord(1, 3))
        self.assertTrue(Record(1, 2) != DerivedRecord(2, 2))
        self.assertTrue(Record(1, 2) != DerivedRecord(3, 4))


    def test_rightHandArgumentImplementsEquality(self):
        """
        The right-hand argument to the equality operator is given a chance
        to determine the result of the operation if it is of a type
        unrelated to the L{FancyEqMixin}-based instance on the left-hand
        side.
        """
        self.assertTrue(Record(1, 2) == EqualToEverything())
        self.assertFalse(Record(1, 2) == EqualToNothing())


    def test_rightHandArgumentImplementsUnequality(self):
        """
        The right-hand argument to the non-equality operator is given a
        chance to determine the result of the operation if it is of a type
        unrelated to the L{FancyEqMixin}-based instance on the left-hand
        side.
        """
        self.assertFalse(Record(1, 2) != EqualToEverything())
        self.assertTrue(Record(1, 2) != EqualToNothing())



class RunAsEffectiveUserTests(unittest.TestCase):
    """
    Test for the L{util.runAsEffectiveUser} function.
    """

    if getattr(os, "geteuid", None) is None:
        skip = "geteuid/seteuid not available"

    def setUp(self):
        self.mockos = MockOS()
        self.patch(os, "geteuid", self.mockos.geteuid)
        self.patch(os, "getegid", self.mockos.getegid)
        self.patch(os, "seteuid", self.mockos.seteuid)
        self.patch(os, "setegid", self.mockos.setegid)


    def _securedFunction(self, startUID, startGID, wantUID, wantGID):
        """
        Check if wanted UID/GID matched start or saved ones.
        """
        self.assertTrue(wantUID == startUID or
                        wantUID == self.mockos.seteuidCalls[-1])
        self.assertTrue(wantGID == startGID or
                        wantGID == self.mockos.setegidCalls[-1])


    def test_forwardResult(self):
        """
        L{util.runAsEffectiveUser} forwards the result obtained by calling the
        given function
        """
        result = util.runAsEffectiveUser(0, 0, lambda: 1)
        self.assertEquals(result, 1)


    def test_takeParameters(self):
        """
        L{util.runAsEffectiveUser} pass the given parameters to the given
        function.
        """
        result = util.runAsEffectiveUser(0, 0, lambda x: 2*x, 3)
        self.assertEquals(result, 6)


    def test_takesKeyworkArguments(self):
        """
        L{util.runAsEffectiveUser} pass the keyword parameters to the given
        function.
        """
        result = util.runAsEffectiveUser(0, 0, lambda x, y=1, z=1: x*y*z, 2, z=3)
        self.assertEquals(result, 6)


    def _testUIDGIDSwitch(self, startUID, startGID, wantUID, wantGID,
                          expectedUIDSwitches, expectedGIDSwitches):
        """
        Helper method checking the calls to C{os.seteuid} and C{os.setegid}
        made by L{util.runAsEffectiveUser}, when switching from startUID to
        wantUID and from startGID to wantGID.
        """
        self.mockos.euid = startUID
        self.mockos.egid = startGID
        util.runAsEffectiveUser(
            wantUID, wantGID,
            self._securedFunction, startUID, startGID, wantUID, wantGID)
        self.assertEquals(self.mockos.seteuidCalls, expectedUIDSwitches)
        self.assertEquals(self.mockos.setegidCalls, expectedGIDSwitches)
        self.mockos.seteuidCalls = []
        self.mockos.setegidCalls = []


    def test_root(self):
        """
        Check UID/GID switches when current effective UID is root.
        """
        self._testUIDGIDSwitch(0, 0, 0, 0, [], [])
        self._testUIDGIDSwitch(0, 0, 1, 0, [1, 0], [])
        self._testUIDGIDSwitch(0, 0, 0, 1, [], [1, 0])
        self._testUIDGIDSwitch(0, 0, 1, 1, [1, 0], [1, 0])


    def test_UID(self):
        """
        Check UID/GID switches when current effective UID is non-root.
        """
        self._testUIDGIDSwitch(1, 0, 0, 0, [0, 1], [])
        self._testUIDGIDSwitch(1, 0, 1, 0, [], [])
        self._testUIDGIDSwitch(1, 0, 1, 1, [0, 1, 0, 1], [1, 0])
        self._testUIDGIDSwitch(1, 0, 2, 1, [0, 2, 0, 1], [1, 0])


    def test_GID(self):
        """
        Check UID/GID switches when current effective GID is non-root.
        """
        self._testUIDGIDSwitch(0, 1, 0, 0, [], [0, 1])
        self._testUIDGIDSwitch(0, 1, 0, 1, [], [])
        self._testUIDGIDSwitch(0, 1, 1, 1, [1, 0], [])
        self._testUIDGIDSwitch(0, 1, 1, 2, [1, 0], [2, 1])


    def test_UIDGID(self):
        """
        Check UID/GID switches when current effective UID/GID is non-root.
        """
        self._testUIDGIDSwitch(1, 1, 0, 0, [0, 1], [0, 1])
        self._testUIDGIDSwitch(1, 1, 0, 1, [0, 1], [])
        self._testUIDGIDSwitch(1, 1, 1, 0, [0, 1, 0, 1], [0, 1])
        self._testUIDGIDSwitch(1, 1, 1, 1, [], [])
        self._testUIDGIDSwitch(1, 1, 2, 1, [0, 2, 0, 1], [])
        self._testUIDGIDSwitch(1, 1, 1, 2, [0, 1, 0, 1], [2, 1])
        self._testUIDGIDSwitch(1, 1, 2, 2, [0, 2, 0, 1], [2, 1])



class UnsignedIDTests(unittest.TestCase):
    """
    Tests for L{util.unsignedID} and L{util.setIDFunction}.
    """
    def setUp(self):
        """
        Save the value of L{util._idFunction} and arrange for it to be restored
        after the test runs.
        """
        self.addCleanup(setattr, util, '_idFunction', util._idFunction)


    def test_setIDFunction(self):
        """
        L{util.setIDFunction} returns the last value passed to it.
        """
        value = object()
        previous = util.setIDFunction(value)
        result = util.setIDFunction(previous)
        self.assertIdentical(value, result)


    def test_unsignedID(self):
        """
        L{util.unsignedID} uses the function passed to L{util.setIDFunction} to
        determine the unique integer id of an object and then adjusts it to be
        positive if necessary.
        """
        foo = object()
        bar = object()

        # A fake object identity mapping
        objects = {foo: 17, bar: -73}
        def fakeId(obj):
            return objects[obj]

        util.setIDFunction(fakeId)

        self.assertEquals(util.unsignedID(foo), 17)
        self.assertEquals(util.unsignedID(bar), (sys.maxint + 1) * 2 - 73)


    def test_defaultIDFunction(self):
        """
        L{util.unsignedID} uses the built in L{id} by default.
        """
        obj = object()
        idValue = id(obj)
        if idValue < 0:
            idValue += (sys.maxint + 1) * 2

        self.assertEquals(util.unsignedID(obj), idValue)



class InitGroupsTests(unittest.TestCase):
    """
    Tests for L{util.initgroups}.
    """

    if pwd is None:
        skip = "pwd not available"


    def setUp(self):
        self.addCleanup(setattr, util, "_c_initgroups", util._c_initgroups)
        self.addCleanup(setattr, util, "setgroups", util.setgroups)


    def test_initgroupsForceC(self):
        """
        If we fake the presence of the C extension, it's called instead of the
        Python implementation.
        """
        calls = []
        util._c_initgroups = lambda x, y: calls.append((x, y))
        setgroupsCalls = []
        util.setgroups = calls.append

        util.initgroups(os.getuid(), 4)
        self.assertEquals(calls, [(pwd.getpwuid(os.getuid())[0], 4)])
        self.assertFalse(setgroupsCalls)


    def test_initgroupsForcePython(self):
        """
        If we fake the absence of the C extension, the Python implementation is
        called instead, calling C{os.setgroups}.
        """
        util._c_initgroups = None
        calls = []
        util.setgroups = calls.append
        util.initgroups(os.getuid(), os.getgid())
        # Something should be in the calls, we don't really care what
        self.assertTrue(calls)


    def test_initgroupsInC(self):
        """
        If the C extension is present, it's called instead of the Python
        version.  We check that by making sure C{os.setgroups} is not called.
        """
        calls = []
        util.setgroups = calls.append
        try:
            util.initgroups(os.getuid(), os.getgid())
        except OSError:
            pass
        self.assertFalse(calls)


    if util._c_initgroups is None:
        test_initgroupsInC.skip = "C initgroups not available"
