# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Test cases for failure module.
"""

import re
import sys
import StringIO
import traceback
import pdb

from twisted.trial import unittest, util

from twisted.python import failure

try:
    from twisted.test import raiser
except ImportError:
    raiser = None


def getDivisionFailure(*args, **kwargs):
    """
    Make a C{Failure} of a divide-by-zero error.

    @param args: Any C{*args} are passed to Failure's constructor.
    @param kwargs: Any C{**kwargs} are passed to Failure's constructor.
    """
    try:
        1/0
    except:
        f = failure.Failure(*args, **kwargs)
    return f


class FailureTestCase(unittest.TestCase):

    def testFailAndTrap(self):
        """Trapping a failure."""
        try:
            raise NotImplementedError('test')
        except:
            f = failure.Failure()
        error = f.trap(SystemExit, RuntimeError)
        self.assertEqual(error, RuntimeError)
        self.assertEqual(f.type, NotImplementedError)


    def test_notTrapped(self):
        """Making sure trap doesn't trap what it shouldn't."""
        try:
            raise ValueError()
        except:
            f = failure.Failure()
        self.assertRaises(failure.Failure, f.trap, OverflowError)


    def assertStartsWith(self, s, prefix):
        """
        Assert that s starts with a particular prefix.
        """
        self.assertTrue(s.startswith(prefix),
                        '%r is not the start of %r' % (prefix, s))


    def test_printingSmokeTest(self):
        """
        None of the print* methods fail when called.
        """
        f = getDivisionFailure()
        out = StringIO.StringIO()
        f.printDetailedTraceback(out)
        self.assertStartsWith(out.getvalue(), '*--- Failure')
        out = StringIO.StringIO()
        f.printBriefTraceback(out)
        self.assertStartsWith(out.getvalue(), 'Traceback')
        out = StringIO.StringIO()
        f.printTraceback(out)
        self.assertStartsWith(out.getvalue(), 'Traceback')


    def test_printingCapturedVarsSmokeTest(self):
        """
        None of the print* methods fail when called on a L{Failure} constructed
        with C{captureVars=True}.

        Local variables on the stack can be seen in the detailed traceback.
        """
        exampleLocalVar = 'xyzzy'
        f = getDivisionFailure(captureVars=True)
        out = StringIO.StringIO()
        f.printDetailedTraceback(out)
        self.assertStartsWith(out.getvalue(), '*--- Failure')
        self.assertNotEqual(None, re.search('exampleLocalVar.*xyzzy',
                                            out.getvalue()))
        out = StringIO.StringIO()
        f.printBriefTraceback(out)
        self.assertStartsWith(out.getvalue(), 'Traceback')
        out = StringIO.StringIO()
        f.printTraceback(out)
        self.assertStartsWith(out.getvalue(), 'Traceback')


    def test_printingCapturedVarsCleanedSmokeTest(self):
        """
        C{printDetailedTraceback} includes information about local variables on
        the stack after C{cleanFailure} has been called.
        """
        exampleLocalVar = 'xyzzy'
        f = getDivisionFailure(captureVars=True)
        f.cleanFailure()
        out = StringIO.StringIO()
        f.printDetailedTraceback(out)
        self.assertNotEqual(None, re.search('exampleLocalVar.*xyzzy',
                                            out.getvalue()))


    def test_printingNoVars(self):
        """
        Calling C{Failure()} with no arguments does not capture any locals or
        globals, so L{printDetailedTraceback} cannot show them in its output.
        """
        out = StringIO.StringIO()
        f = getDivisionFailure()
        f.printDetailedTraceback(out)
        # There should be no variables in the detailed output.  Variables are
        # printed on lines with 2 leading spaces.
        linesWithVars = [line for line in out.getvalue().splitlines()
                         if line.startswith('  ')]
        self.assertEqual([], linesWithVars)
        self.assertSubstring(
            'Capture of Locals and Globals disabled', out.getvalue())


    def test_printingCaptureVars(self):
        """
        Calling C{Failure(captureVars=True)} captures the locals and globals
        for its stack frames, so L{printDetailedTraceback} will show them in
        its output.
        """
        out = StringIO.StringIO()
        f = getDivisionFailure(captureVars=True)
        f.printDetailedTraceback(out)
        # Variables are printed on lines with 2 leading spaces.
        linesWithVars = [line for line in out.getvalue().splitlines()
                         if line.startswith('  ')]
        self.assertNotEqual([], linesWithVars)


    def testExplictPass(self):
        e = RuntimeError()
        f = failure.Failure(e)
        f.trap(RuntimeError)
        self.assertEqual(f.value, e)


    def _getInnermostFrameLine(self, f):
        try:
            f.raiseException()
        except ZeroDivisionError:
            tb = traceback.extract_tb(sys.exc_info()[2])
            return tb[-1][-1]
        else:
            raise Exception(
                "f.raiseException() didn't raise ZeroDivisionError!?")


    def testRaiseExceptionWithTB(self):
        f = getDivisionFailure()
        innerline = self._getInnermostFrameLine(f)
        self.assertEqual(innerline, '1/0')


    def testLackOfTB(self):
        f = getDivisionFailure()
        f.cleanFailure()
        innerline = self._getInnermostFrameLine(f)
        self.assertEqual(innerline, '1/0')

    testLackOfTB.todo = "the traceback is not preserved, exarkun said he'll try to fix this! god knows how"


    _stringException = "bugger off"
    def _getStringFailure(self):
        try:
            raise self._stringException
        except:
            f = failure.Failure()
        return f


    def test_raiseStringExceptions(self):
        # String exceptions used to totally bugged f.raiseException
        f = self._getStringFailure()
        try:
            f.raiseException()
        except:
            self.assertEqual(sys.exc_info()[0], self._stringException)
        else:
            raise AssertionError("Should have raised")
    test_raiseStringExceptions.suppress = [
        util.suppress(message='raising a string exception is deprecated')]


    def test_printStringExceptions(self):
        """
        L{Failure.printTraceback} should write out stack and exception
        information, even for string exceptions.
        """
        failure = self._getStringFailure()
        output = StringIO.StringIO()
        failure.printTraceback(file=output)
        lines = output.getvalue().splitlines()
        # The last line should be the value of the raised string
        self.assertEqual(lines[-1], self._stringException)

    test_printStringExceptions.suppress = [
        util.suppress(message='raising a string exception is deprecated')]

    if sys.version_info[:2] >= (2, 6):
        skipMsg = ("String exceptions aren't supported anymore starting "
                   "Python 2.6")
        test_raiseStringExceptions.skip = skipMsg
        test_printStringExceptions.skip = skipMsg


    def testConstructionFails(self):
        """
        Creating a Failure with no arguments causes it to try to discover the
        current interpreter exception state.  If no such state exists, creating
        the Failure should raise a synchronous exception.
        """
        self.assertRaises(failure.NoCurrentExceptionError, failure.Failure)


    def test_getTracebackObject(self):
        """
        If the C{Failure} has not been cleaned, then C{getTracebackObject}
        returns the traceback object that captured in its constructor.
        """
        f = getDivisionFailure()
        self.assertEqual(f.getTracebackObject(), f.tb)


    def test_getTracebackObjectFromCaptureVars(self):
        """
        C{captureVars=True} has no effect on the result of
        C{getTracebackObject}.
        """
        try:
            1/0
        except ZeroDivisionError:
            noVarsFailure = failure.Failure()
            varsFailure = failure.Failure(captureVars=True)
        self.assertEqual(noVarsFailure.getTracebackObject(), varsFailure.tb)


    def test_getTracebackObjectFromClean(self):
        """
        If the Failure has been cleaned, then C{getTracebackObject} returns an
        object that looks the same to L{traceback.extract_tb}.
        """
        f = getDivisionFailure()
        expected = traceback.extract_tb(f.getTracebackObject())
        f.cleanFailure()
        observed = traceback.extract_tb(f.getTracebackObject())
        self.assertNotEqual(None, expected)
        self.assertEqual(expected, observed)


    def test_getTracebackObjectFromCaptureVarsAndClean(self):
        """
        If the Failure was created with captureVars, then C{getTracebackObject}
        returns an object that looks the same to L{traceback.extract_tb}.
        """
        f = getDivisionFailure(captureVars=True)
        expected = traceback.extract_tb(f.getTracebackObject())
        f.cleanFailure()
        observed = traceback.extract_tb(f.getTracebackObject())
        self.assertEqual(expected, observed)


    def test_getTracebackObjectWithoutTraceback(self):
        """
        L{failure.Failure}s need not be constructed with traceback objects. If
        a C{Failure} has no traceback information at all, C{getTracebackObject}
        just returns None.

        None is a good value, because traceback.extract_tb(None) -> [].
        """
        f = failure.Failure(Exception("some error"))
        self.assertEqual(f.getTracebackObject(), None)



class BrokenStr(Exception):
    """
    An exception class the instances of which cannot be presented as strings via
    C{str}.
    """
    def __str__(self):
        # Could raise something else, but there's no point as yet.
        raise self



class BrokenExceptionMetaclass(type):
    """
    A metaclass for an exception type which cannot be presented as a string via
    C{str}.
    """
    def __str__(self):
        raise ValueError("You cannot make a string out of me.")



class BrokenExceptionType(Exception, object):
    """
    The aforementioned exception type which cnanot be presented as a string via
    C{str}.
    """
    __metaclass__ = BrokenExceptionMetaclass



class GetTracebackTests(unittest.TestCase):
    """
    Tests for L{Failure.getTraceback}.
    """
    def _brokenValueTest(self, detail):
        """
        Construct a L{Failure} with an exception that raises an exception from
        its C{__str__} method and then call C{getTraceback} with the specified
        detail and verify that it returns a string.
        """
        x = BrokenStr()
        f = failure.Failure(x)
        traceback = f.getTraceback(detail=detail)
        self.assertIsInstance(traceback, str)


    def test_brokenValueBriefDetail(self):
        """
        A L{Failure} might wrap an exception with a C{__str__} method which
        raises an exception.  In this case, calling C{getTraceback} on the
        failure with the C{"brief"} detail does not raise an exception.
        """
        self._brokenValueTest("brief")


    def test_brokenValueDefaultDetail(self):
        """
        Like test_brokenValueBriefDetail, but for the C{"default"} detail case.
        """
        self._brokenValueTest("default")


    def test_brokenValueVerboseDetail(self):
        """
        Like test_brokenValueBriefDetail, but for the C{"default"} detail case.
        """
        self._brokenValueTest("verbose")


    def _brokenTypeTest(self, detail):
        """
        Construct a L{Failure} with an exception type that raises an exception
        from its C{__str__} method and then call C{getTraceback} with the
        specified detail and verify that it returns a string.
        """
        f = failure.Failure(BrokenExceptionType())
        traceback = f.getTraceback(detail=detail)
        self.assertIsInstance(traceback, str)


    def test_brokenTypeBriefDetail(self):
        """
        A L{Failure} might wrap an exception the type object of which has a
        C{__str__} method which raises an exception.  In this case, calling
        C{getTraceback} on the failure with the C{"brief"} detail does not raise
        an exception.
        """
        self._brokenTypeTest("brief")


    def test_brokenTypeDefaultDetail(self):
        """
        Like test_brokenTypeBriefDetail, but for the C{"default"} detail case.
        """
        self._brokenTypeTest("default")


    def test_brokenTypeVerboseDetail(self):
        """
        Like test_brokenTypeBriefDetail, but for the C{"verbose"} detail case.
        """
        self._brokenTypeTest("verbose")



class FindFailureTests(unittest.TestCase):
    """
    Tests for functionality related to L{Failure._findFailure}.
    """

    def test_findNoFailureInExceptionHandler(self):
        """
        Within an exception handler, _findFailure should return
        C{None} in case no Failure is associated with the current
        exception.
        """
        try:
            1/0
        except:
            self.assertEqual(failure.Failure._findFailure(), None)
        else:
            self.fail("No exception raised from 1/0!?")


    def test_findNoFailure(self):
        """
        Outside of an exception handler, _findFailure should return None.
        """
        self.assertEqual(sys.exc_info()[-1], None) #environment sanity check
        self.assertEqual(failure.Failure._findFailure(), None)


    def test_findFailure(self):
        """
        Within an exception handler, it should be possible to find the
        original Failure that caused the current exception (if it was
        caused by raiseException).
        """
        f = getDivisionFailure()
        f.cleanFailure()
        try:
            f.raiseException()
        except:
            self.assertEqual(failure.Failure._findFailure(), f)
        else:
            self.fail("No exception raised from raiseException!?")


    def test_failureConstructionFindsOriginalFailure(self):
        """
        When a Failure is constructed in the context of an exception
        handler that is handling an exception raised by
        raiseException, the new Failure should be chained to that
        original Failure.
        """
        f = getDivisionFailure()
        f.cleanFailure()
        try:
            f.raiseException()
        except:
            newF = failure.Failure()
            self.assertEqual(f.getTraceback(), newF.getTraceback())
        else:
            self.fail("No exception raised from raiseException!?")


    def test_failureConstructionWithMungedStackSucceeds(self):
        """
        Pyrex and Cython are known to insert fake stack frames so as to give
        more Python-like tracebacks. These stack frames with empty code objects
        should not break extraction of the exception.
        """
        try:
            raiser.raiseException()
        except raiser.RaiserException:
            f = failure.Failure()
            self.assertTrue(f.check(raiser.RaiserException))
        else:
            self.fail("No exception raised from extension?!")


    if raiser is None:
        skipMsg = "raiser extension not available"
        test_failureConstructionWithMungedStackSucceeds.skip = skipMsg



class TestFormattableTraceback(unittest.TestCase):
    """
    Whitebox tests that show that L{failure._Traceback} constructs objects that
    can be used by L{traceback.extract_tb}.

    If the objects can be used by L{traceback.extract_tb}, then they can be
    formatted using L{traceback.format_tb} and friends.
    """

    def test_singleFrame(self):
        """
        A C{_Traceback} object constructed with a single frame should be able
        to be passed to L{traceback.extract_tb}, and we should get a singleton
        list containing a (filename, lineno, methodname, line) tuple.
        """
        tb = failure._Traceback([['method', 'filename.py', 123, {}, {}]])
        # Note that we don't need to test that extract_tb correctly extracts
        # the line's contents. In this case, since filename.py doesn't exist,
        # it will just use None.
        self.assertEqual(traceback.extract_tb(tb),
                         [('filename.py', 123, 'method', None)])


    def test_manyFrames(self):
        """
        A C{_Traceback} object constructed with multiple frames should be able
        to be passed to L{traceback.extract_tb}, and we should get a list
        containing a tuple for each frame.
        """
        tb = failure._Traceback([
            ['method1', 'filename.py', 123, {}, {}],
            ['method2', 'filename.py', 235, {}, {}]])
        self.assertEqual(traceback.extract_tb(tb),
                         [('filename.py', 123, 'method1', None),
                          ('filename.py', 235, 'method2', None)])



class TestFrameAttributes(unittest.TestCase):
    """
    _Frame objects should possess some basic attributes that qualify them as
    fake python Frame objects.
    """

    def test_fakeFrameAttributes(self):
        """
        L{_Frame} instances have the C{f_globals} and C{f_locals} attributes
        bound to C{dict} instance.  They also have the C{f_code} attribute
        bound to something like a code object.
        """
        frame = failure._Frame("dummyname", "dummyfilename")
        self.assertIsInstance(frame.f_globals, dict)
        self.assertIsInstance(frame.f_locals, dict)
        self.assertIsInstance(frame.f_code, failure._Code)



class TestDebugMode(unittest.TestCase):
    """
    Failure's debug mode should allow jumping into the debugger.
    """

    def setUp(self):
        """
        Override pdb.post_mortem so we can make sure it's called.
        """
        # Make sure any changes we make are reversed:
        post_mortem = pdb.post_mortem
        origInit = failure.Failure.__dict__['__init__']
        def restore():
            pdb.post_mortem = post_mortem
            failure.Failure.__dict__['__init__'] = origInit
        self.addCleanup(restore)

        self.result = []
        pdb.post_mortem = self.result.append
        failure.startDebugMode()


    def test_regularFailure(self):
        """
        If startDebugMode() is called, calling Failure() will first call
        pdb.post_mortem with the traceback.
        """
        try:
            1/0
        except:
            typ, exc, tb = sys.exc_info()
            f = failure.Failure()
        self.assertEqual(self.result, [tb])
        self.assertEqual(f.captureVars, False)


    def test_captureVars(self):
        """
        If startDebugMode() is called, passing captureVars to Failure() will
        not blow up.
        """
        try:
            1/0
        except:
            typ, exc, tb = sys.exc_info()
            f = failure.Failure(captureVars=True)
        self.assertEqual(self.result, [tb])
        self.assertEqual(f.captureVars, True)



if sys.version_info[:2] >= (2, 5):
    from twisted.test.generator_failure_tests import TwoPointFiveFailureTests

# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Test cases for failure module.
"""

import re
import sys
import StringIO
import traceback
import pdb

from twisted.trial import unittest, util

from twisted.python import failure

try:
    from twisted.test import raiser
except ImportError:
    raiser = None


def getDivisionFailure(*args, **kwargs):
    """
    Make a C{Failure} of a divide-by-zero error.

    @param args: Any C{*args} are passed to Failure's constructor.
    @param kwargs: Any C{**kwargs} are passed to Failure's constructor.
    """
    try:
        1/0
    except:
        f = failure.Failure(*args, **kwargs)
    return f


class FailureTestCase(unittest.TestCase):

    def testFailAndTrap(self):
        """Trapping a failure."""
        try:
            raise NotImplementedError('test')
        except:
            f = failure.Failure()
        error = f.trap(SystemExit, RuntimeError)
        self.assertEqual(error, RuntimeError)
        self.assertEqual(f.type, NotImplementedError)


    def test_notTrapped(self):
        """Making sure trap doesn't trap what it shouldn't."""
        try:
            raise ValueError()
        except:
            f = failure.Failure()
        self.assertRaises(failure.Failure, f.trap, OverflowError)


    def assertStartsWith(self, s, prefix):
        """
        Assert that s starts with a particular prefix.
        """
        self.assertTrue(s.startswith(prefix),
                        '%r is not the start of %r' % (prefix, s))


    def test_printingSmokeTest(self):
        """
        None of the print* methods fail when called.
        """
        f = getDivisionFailure()
        out = StringIO.StringIO()
        f.printDetailedTraceback(out)
        self.assertStartsWith(out.getvalue(), '*--- Failure')
        out = StringIO.StringIO()
        f.printBriefTraceback(out)
        self.assertStartsWith(out.getvalue(), 'Traceback')
        out = StringIO.StringIO()
        f.printTraceback(out)
        self.assertStartsWith(out.getvalue(), 'Traceback')


    def test_printingCapturedVarsSmokeTest(self):
        """
        None of the print* methods fail when called on a L{Failure} constructed
        with C{captureVars=True}.

        Local variables on the stack can be seen in the detailed traceback.
        """
        exampleLocalVar = 'xyzzy'
        f = getDivisionFailure(captureVars=True)
        out = StringIO.StringIO()
        f.printDetailedTraceback(out)
        self.assertStartsWith(out.getvalue(), '*--- Failure')
        self.assertNotEqual(None, re.search('exampleLocalVar.*xyzzy',
                                            out.getvalue()))
        out = StringIO.StringIO()
        f.printBriefTraceback(out)
        self.assertStartsWith(out.getvalue(), 'Traceback')
        out = StringIO.StringIO()
        f.printTraceback(out)
        self.assertStartsWith(out.getvalue(), 'Traceback')


    def test_printingCapturedVarsCleanedSmokeTest(self):
        """
        C{printDetailedTraceback} includes information about local variables on
        the stack after C{cleanFailure} has been called.
        """
        exampleLocalVar = 'xyzzy'
        f = getDivisionFailure(captureVars=True)
        f.cleanFailure()
        out = StringIO.StringIO()
        f.printDetailedTraceback(out)
        self.assertNotEqual(None, re.search('exampleLocalVar.*xyzzy',
                                            out.getvalue()))


    def test_printingNoVars(self):
        """
        Calling C{Failure()} with no arguments does not capture any locals or
        globals, so L{printDetailedTraceback} cannot show them in its output.
        """
        out = StringIO.StringIO()
        f = getDivisionFailure()
        f.printDetailedTraceback(out)
        # There should be no variables in the detailed output.  Variables are
        # printed on lines with 2 leading spaces.
        linesWithVars = [line for line in out.getvalue().splitlines()
                         if line.startswith('  ')]
        self.assertEqual([], linesWithVars)
        self.assertSubstring(
            'Capture of Locals and Globals disabled', out.getvalue())


    def test_printingCaptureVars(self):
        """
        Calling C{Failure(captureVars=True)} captures the locals and globals
        for its stack frames, so L{printDetailedTraceback} will show them in
        its output.
        """
        out = StringIO.StringIO()
        f = getDivisionFailure(captureVars=True)
        f.printDetailedTraceback(out)
        # Variables are printed on lines with 2 leading spaces.
        linesWithVars = [line for line in out.getvalue().splitlines()
                         if line.startswith('  ')]
        self.assertNotEqual([], linesWithVars)


    def testExplictPass(self):
        e = RuntimeError()
        f = failure.Failure(e)
        f.trap(RuntimeError)
        self.assertEqual(f.value, e)


    def _getInnermostFrameLine(self, f):
        try:
            f.raiseException()
        except ZeroDivisionError:
            tb = traceback.extract_tb(sys.exc_info()[2])
            return tb[-1][-1]
        else:
            raise Exception(
                "f.raiseException() didn't raise ZeroDivisionError!?")


    def testRaiseExceptionWithTB(self):
        f = getDivisionFailure()
        innerline = self._getInnermostFrameLine(f)
        self.assertEqual(innerline, '1/0')


    def testLackOfTB(self):
        f = getDivisionFailure()
        f.cleanFailure()
        innerline = self._getInnermostFrameLine(f)
        self.assertEqual(innerline, '1/0')

    testLackOfTB.todo = "the traceback is not preserved, exarkun said he'll try to fix this! god knows how"


    _stringException = "bugger off"
    def _getStringFailure(self):
        try:
            raise self._stringException
        except:
            f = failure.Failure()
        return f


    def test_raiseStringExceptions(self):
        # String exceptions used to totally bugged f.raiseException
        f = self._getStringFailure()
        try:
            f.raiseException()
        except:
            self.assertEqual(sys.exc_info()[0], self._stringException)
        else:
            raise AssertionError("Should have raised")
    test_raiseStringExceptions.suppress = [
        util.suppress(message='raising a string exception is deprecated')]


    def test_printStringExceptions(self):
        """
        L{Failure.printTraceback} should write out stack and exception
        information, even for string exceptions.
        """
        failure = self._getStringFailure()
        output = StringIO.StringIO()
        failure.printTraceback(file=output)
        lines = output.getvalue().splitlines()
        # The last line should be the value of the raised string
        self.assertEqual(lines[-1], self._stringException)

    test_printStringExceptions.suppress = [
        util.suppress(message='raising a string exception is deprecated')]

    if sys.version_info[:2] >= (2, 6):
        skipMsg = ("String exceptions aren't supported anymore starting "
                   "Python 2.6")
        test_raiseStringExceptions.skip = skipMsg
        test_printStringExceptions.skip = skipMsg


    def testConstructionFails(self):
        """
        Creating a Failure with no arguments causes it to try to discover the
        current interpreter exception state.  If no such state exists, creating
        the Failure should raise a synchronous exception.
        """
        self.assertRaises(failure.NoCurrentExceptionError, failure.Failure)


    def test_getTracebackObject(self):
        """
        If the C{Failure} has not been cleaned, then C{getTracebackObject}
        returns the traceback object that captured in its constructor.
        """
        f = getDivisionFailure()
        self.assertEqual(f.getTracebackObject(), f.tb)


    def test_getTracebackObjectFromCaptureVars(self):
        """
        C{captureVars=True} has no effect on the result of
        C{getTracebackObject}.
        """
        try:
            1/0
        except ZeroDivisionError:
            noVarsFailure = failure.Failure()
            varsFailure = failure.Failure(captureVars=True)
        self.assertEqual(noVarsFailure.getTracebackObject(), varsFailure.tb)


    def test_getTracebackObjectFromClean(self):
        """
        If the Failure has been cleaned, then C{getTracebackObject} returns an
        object that looks the same to L{traceback.extract_tb}.
        """
        f = getDivisionFailure()
        expected = traceback.extract_tb(f.getTracebackObject())
        f.cleanFailure()
        observed = traceback.extract_tb(f.getTracebackObject())
        self.assertNotEqual(None, expected)
        self.assertEqual(expected, observed)


    def test_getTracebackObjectFromCaptureVarsAndClean(self):
        """
        If the Failure was created with captureVars, then C{getTracebackObject}
        returns an object that looks the same to L{traceback.extract_tb}.
        """
        f = getDivisionFailure(captureVars=True)
        expected = traceback.extract_tb(f.getTracebackObject())
        f.cleanFailure()
        observed = traceback.extract_tb(f.getTracebackObject())
        self.assertEqual(expected, observed)


    def test_getTracebackObjectWithoutTraceback(self):
        """
        L{failure.Failure}s need not be constructed with traceback objects. If
        a C{Failure} has no traceback information at all, C{getTracebackObject}
        just returns None.

        None is a good value, because traceback.extract_tb(None) -> [].
        """
        f = failure.Failure(Exception("some error"))
        self.assertEqual(f.getTracebackObject(), None)



class BrokenStr(Exception):
    """
    An exception class the instances of which cannot be presented as strings via
    C{str}.
    """
    def __str__(self):
        # Could raise something else, but there's no point as yet.
        raise self



class BrokenExceptionMetaclass(type):
    """
    A metaclass for an exception type which cannot be presented as a string via
    C{str}.
    """
    def __str__(self):
        raise ValueError("You cannot make a string out of me.")



class BrokenExceptionType(Exception, object):
    """
    The aforementioned exception type which cnanot be presented as a string via
    C{str}.
    """
    __metaclass__ = BrokenExceptionMetaclass



class GetTracebackTests(unittest.TestCase):
    """
    Tests for L{Failure.getTraceback}.
    """
    def _brokenValueTest(self, detail):
        """
        Construct a L{Failure} with an exception that raises an exception from
        its C{__str__} method and then call C{getTraceback} with the specified
        detail and verify that it returns a string.
        """
        x = BrokenStr()
        f = failure.Failure(x)
        traceback = f.getTraceback(detail=detail)
        self.assertIsInstance(traceback, str)


    def test_brokenValueBriefDetail(self):
        """
        A L{Failure} might wrap an exception with a C{__str__} method which
        raises an exception.  In this case, calling C{getTraceback} on the
        failure with the C{"brief"} detail does not raise an exception.
        """
        self._brokenValueTest("brief")


    def test_brokenValueDefaultDetail(self):
        """
        Like test_brokenValueBriefDetail, but for the C{"default"} detail case.
        """
        self._brokenValueTest("default")


    def test_brokenValueVerboseDetail(self):
        """
        Like test_brokenValueBriefDetail, but for the C{"default"} detail case.
        """
        self._brokenValueTest("verbose")


    def _brokenTypeTest(self, detail):
        """
        Construct a L{Failure} with an exception type that raises an exception
        from its C{__str__} method and then call C{getTraceback} with the
        specified detail and verify that it returns a string.
        """
        f = failure.Failure(BrokenExceptionType())
        traceback = f.getTraceback(detail=detail)
        self.assertIsInstance(traceback, str)


    def test_brokenTypeBriefDetail(self):
        """
        A L{Failure} might wrap an exception the type object of which has a
        C{__str__} method which raises an exception.  In this case, calling
        C{getTraceback} on the failure with the C{"brief"} detail does not raise
        an exception.
        """
        self._brokenTypeTest("brief")


    def test_brokenTypeDefaultDetail(self):
        """
        Like test_brokenTypeBriefDetail, but for the C{"default"} detail case.
        """
        self._brokenTypeTest("default")


    def test_brokenTypeVerboseDetail(self):
        """
        Like test_brokenTypeBriefDetail, but for the C{"verbose"} detail case.
        """
        self._brokenTypeTest("verbose")



class FindFailureTests(unittest.TestCase):
    """
    Tests for functionality related to L{Failure._findFailure}.
    """

    def test_findNoFailureInExceptionHandler(self):
        """
        Within an exception handler, _findFailure should return
        C{None} in case no Failure is associated with the current
        exception.
        """
        try:
            1/0
        except:
            self.assertEqual(failure.Failure._findFailure(), None)
        else:
            self.fail("No exception raised from 1/0!?")


    def test_findNoFailure(self):
        """
        Outside of an exception handler, _findFailure should return None.
        """
        self.assertEqual(sys.exc_info()[-1], None) #environment sanity check
        self.assertEqual(failure.Failure._findFailure(), None)


    def test_findFailure(self):
        """
        Within an exception handler, it should be possible to find the
        original Failure that caused the current exception (if it was
        caused by raiseException).
        """
        f = getDivisionFailure()
        f.cleanFailure()
        try:
            f.raiseException()
        except:
            self.assertEqual(failure.Failure._findFailure(), f)
        else:
            self.fail("No exception raised from raiseException!?")


    def test_failureConstructionFindsOriginalFailure(self):
        """
        When a Failure is constructed in the context of an exception
        handler that is handling an exception raised by
        raiseException, the new Failure should be chained to that
        original Failure.
        """
        f = getDivisionFailure()
        f.cleanFailure()
        try:
            f.raiseException()
        except:
            newF = failure.Failure()
            self.assertEqual(f.getTraceback(), newF.getTraceback())
        else:
            self.fail("No exception raised from raiseException!?")


    def test_failureConstructionWithMungedStackSucceeds(self):
        """
        Pyrex and Cython are known to insert fake stack frames so as to give
        more Python-like tracebacks. These stack frames with empty code objects
        should not break extraction of the exception.
        """
        try:
            raiser.raiseException()
        except raiser.RaiserException:
            f = failure.Failure()
            self.assertTrue(f.check(raiser.RaiserException))
        else:
            self.fail("No exception raised from extension?!")


    if raiser is None:
        skipMsg = "raiser extension not available"
        test_failureConstructionWithMungedStackSucceeds.skip = skipMsg



class TestFormattableTraceback(unittest.TestCase):
    """
    Whitebox tests that show that L{failure._Traceback} constructs objects that
    can be used by L{traceback.extract_tb}.

    If the objects can be used by L{traceback.extract_tb}, then they can be
    formatted using L{traceback.format_tb} and friends.
    """

    def test_singleFrame(self):
        """
        A C{_Traceback} object constructed with a single frame should be able
        to be passed to L{traceback.extract_tb}, and we should get a singleton
        list containing a (filename, lineno, methodname, line) tuple.
        """
        tb = failure._Traceback([['method', 'filename.py', 123, {}, {}]])
        # Note that we don't need to test that extract_tb correctly extracts
        # the line's contents. In this case, since filename.py doesn't exist,
        # it will just use None.
        self.assertEqual(traceback.extract_tb(tb),
                         [('filename.py', 123, 'method', None)])


    def test_manyFrames(self):
        """
        A C{_Traceback} object constructed with multiple frames should be able
        to be passed to L{traceback.extract_tb}, and we should get a list
        containing a tuple for each frame.
        """
        tb = failure._Traceback([
            ['method1', 'filename.py', 123, {}, {}],
            ['method2', 'filename.py', 235, {}, {}]])
        self.assertEqual(traceback.extract_tb(tb),
                         [('filename.py', 123, 'method1', None),
                          ('filename.py', 235, 'method2', None)])



class TestFrameAttributes(unittest.TestCase):
    """
    _Frame objects should possess some basic attributes that qualify them as
    fake python Frame objects.
    """

    def test_fakeFrameAttributes(self):
        """
        L{_Frame} instances have the C{f_globals} and C{f_locals} attributes
        bound to C{dict} instance.  They also have the C{f_code} attribute
        bound to something like a code object.
        """
        frame = failure._Frame("dummyname", "dummyfilename")
        self.assertIsInstance(frame.f_globals, dict)
        self.assertIsInstance(frame.f_locals, dict)
        self.assertIsInstance(frame.f_code, failure._Code)



class TestDebugMode(unittest.TestCase):
    """
    Failure's debug mode should allow jumping into the debugger.
    """

    def setUp(self):
        """
        Override pdb.post_mortem so we can make sure it's called.
        """
        # Make sure any changes we make are reversed:
        post_mortem = pdb.post_mortem
        origInit = failure.Failure.__dict__['__init__']
        def restore():
            pdb.post_mortem = post_mortem
            failure.Failure.__dict__['__init__'] = origInit
        self.addCleanup(restore)

        self.result = []
        pdb.post_mortem = self.result.append
        failure.startDebugMode()


    def test_regularFailure(self):
        """
        If startDebugMode() is called, calling Failure() will first call
        pdb.post_mortem with the traceback.
        """
        try:
            1/0
        except:
            typ, exc, tb = sys.exc_info()
            f = failure.Failure()
        self.assertEqual(self.result, [tb])
        self.assertEqual(f.captureVars, False)


    def test_captureVars(self):
        """
        If startDebugMode() is called, passing captureVars to Failure() will
        not blow up.
        """
        try:
            1/0
        except:
            typ, exc, tb = sys.exc_info()
            f = failure.Failure(captureVars=True)
        self.assertEqual(self.result, [tb])
        self.assertEqual(f.captureVars, True)



if sys.version_info[:2] >= (2, 5):
    from twisted.test.generator_failure_tests import TwoPointFiveFailureTests

# Copyright (c) Twisted Matrix Laboratories. # See LICENSE for details. Test cases for failure module. Make a C{Failure} of a divide-by-zero error.      @param args: Any C{*args} are passed to Failure's constructor.     @param kwargs: Any C{**kwargs} are passed to Failure's constructor. Trapping a failure. Making sure trap doesn't trap what it shouldn't. Assert that s starts with a particular prefix. None of the print* methods fail when called. None of the print* methods fail when called on a L{Failure} constructed         with C{captureVars=True}.          Local variables on the stack can be seen in the detailed traceback. C{printDetailedTraceback} includes information about local variables on         the stack after C{cleanFailure} has been called. Calling C{Failure()} with no arguments does not capture any locals or         globals, so L{printDetailedTraceback} cannot show them in its output. # There should be no variables in the detailed output.  Variables are # printed on lines with 2 leading spaces. Calling C{Failure(captureVars=True)} captures the locals and globals         for its stack frames, so L{printDetailedTraceback} will show them in         its output. # Variables are printed on lines with 2 leading spaces. # String exceptions used to totally bugged f.raiseException L{Failure.printTraceback} should write out stack and exception         information, even for string exceptions. # The last line should be the value of the raised string Creating a Failure with no arguments causes it to try to discover the         current interpreter exception state.  If no such state exists, creating         the Failure should raise a synchronous exception. If the C{Failure} has not been cleaned, then C{getTracebackObject}         returns the traceback object that captured in its constructor. C{captureVars=True} has no effect on the result of         C{getTracebackObject}. If the Failure has been cleaned, then C{getTracebackObject} returns an         object that looks the same to L{traceback.extract_tb}. If the Failure was created with captureVars, then C{getTracebackObject}         returns an object that looks the same to L{traceback.extract_tb}. L{failure.Failure}s need not be constructed with traceback objects. If         a C{Failure} has no traceback information at all, C{getTracebackObject}         just returns None.          None is a good value, because traceback.extract_tb(None) -> []. An exception class the instances of which cannot be presented as strings via     C{str}. # Could raise something else, but there's no point as yet. A metaclass for an exception type which cannot be presented as a string via     C{str}. The aforementioned exception type which cnanot be presented as a string via     C{str}. Tests for L{Failure.getTraceback}. Construct a L{Failure} with an exception that raises an exception from         its C{__str__} method and then call C{getTraceback} with the specified         detail and verify that it returns a string. A L{Failure} might wrap an exception with a C{__str__} method which         raises an exception.  In this case, calling C{getTraceback} on the         failure with the C{"brief"} detail does not raise an exception. Like test_brokenValueBriefDetail, but for the C{"default"} detail case. Like test_brokenValueBriefDetail, but for the C{"default"} detail case. Construct a L{Failure} with an exception type that raises an exception         from its C{__str__} method and then call C{getTraceback} with the         specified detail and verify that it returns a string. A L{Failure} might wrap an exception the type object of which has a         C{__str__} method which raises an exception.  In this case, calling         C{getTraceback} on the failure with the C{"brief"} detail does not raise         an exception. Like test_brokenTypeBriefDetail, but for the C{"default"} detail case. Like test_brokenTypeBriefDetail, but for the C{"verbose"} detail case. Tests for functionality related to L{Failure._findFailure}. Within an exception handler, _findFailure should return         C{None} in case no Failure is associated with the current         exception. Outside of an exception handler, _findFailure should return None. #environment sanity check Within an exception handler, it should be possible to find the         original Failure that caused the current exception (if it was         caused by raiseException). When a Failure is constructed in the context of an exception         handler that is handling an exception raised by         raiseException, the new Failure should be chained to that         original Failure. Pyrex and Cython are known to insert fake stack frames so as to give         more Python-like tracebacks. These stack frames with empty code objects         should not break extraction of the exception. Whitebox tests that show that L{failure._Traceback} constructs objects that     can be used by L{traceback.extract_tb}.      If the objects can be used by L{traceback.extract_tb}, then they can be     formatted using L{traceback.format_tb} and friends. A C{_Traceback} object constructed with a single frame should be able         to be passed to L{traceback.extract_tb}, and we should get a singleton         list containing a (filename, lineno, methodname, line) tuple. # Note that we don't need to test that extract_tb correctly extracts # the line's contents. In this case, since filename.py doesn't exist, # it will just use None. A C{_Traceback} object constructed with multiple frames should be able         to be passed to L{traceback.extract_tb}, and we should get a list         containing a tuple for each frame. _Frame objects should possess some basic attributes that qualify them as     fake python Frame objects. L{_Frame} instances have the C{f_globals} and C{f_locals} attributes         bound to C{dict} instance.  They also have the C{f_code} attribute         bound to something like a code object. Failure's debug mode should allow jumping into the debugger. Override pdb.post_mortem so we can make sure it's called. # Make sure any changes we make are reversed: If startDebugMode() is called, calling Failure() will first call         pdb.post_mortem with the traceback. If startDebugMode() is called, passing captureVars to Failure() will         not blow up.