Your IP : 172.28.240.42
# 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