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# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Tests for Trial's interaction with the Python warning system.
"""
import sys, warnings
from StringIO import StringIO
from twisted.python.filepath import FilePath
from twisted.trial.unittest import TestCase, _collectWarnings
from twisted.trial.reporter import TestResult
class Mask(object):
"""
Hide a L{TestCase} definition from trial's automatic discovery mechanism.
"""
class MockTests(TestCase):
"""
A test case which is used by L{FlushWarningsTests} to verify behavior
which cannot be verified by code inside a single test method.
"""
message = "some warning text"
category = UserWarning
def test_unflushed(self):
"""
Generate a warning and don't flush it.
"""
warnings.warn(self.message, self.category)
def test_flushed(self):
"""
Generate a warning and flush it.
"""
warnings.warn(self.message, self.category)
self.assertEqual(len(self.flushWarnings()), 1)
class FlushWarningsTests(TestCase):
"""
Tests for L{TestCase.flushWarnings}, an API for examining the warnings
emitted so far in a test.
"""
def assertDictSubset(self, set, subset):
"""
Assert that all the keys present in C{subset} are also present in
C{set} and that the corresponding values are equal.
"""
for k, v in subset.iteritems():
self.assertEqual(set[k], v)
def assertDictSubsets(self, sets, subsets):
"""
For each pair of corresponding elements in C{sets} and C{subsets},
assert that the element from C{subsets} is a subset of the element from
C{sets}.
"""
self.assertEqual(len(sets), len(subsets))
for a, b in zip(sets, subsets):
self.assertDictSubset(a, b)
def test_none(self):
"""
If no warnings are emitted by a test, L{TestCase.flushWarnings} returns
an empty list.
"""
self.assertEqual(self.flushWarnings(), [])
def test_several(self):
"""
If several warnings are emitted by a test, L{TestCase.flushWarnings}
returns a list containing all of them.
"""
firstMessage = "first warning message"
firstCategory = UserWarning
warnings.warn(message=firstMessage, category=firstCategory)
secondMessage = "second warning message"
secondCategory = RuntimeWarning
warnings.warn(message=secondMessage, category=secondCategory)
self.assertDictSubsets(
self.flushWarnings(),
[{'category': firstCategory, 'message': firstMessage},
{'category': secondCategory, 'message': secondMessage}])
def test_repeated(self):
"""
The same warning triggered twice from the same place is included twice
in the list returned by L{TestCase.flushWarnings}.
"""
message = "the message"
category = RuntimeWarning
for i in range(2):
warnings.warn(message=message, category=category)
self.assertDictSubsets(
self.flushWarnings(),
[{'category': category, 'message': message}] * 2)
def test_cleared(self):
"""
After a particular warning event has been returned by
L{TestCase.flushWarnings}, it is not returned by subsequent calls.
"""
message = "the message"
category = RuntimeWarning
warnings.warn(message=message, category=category)
self.assertDictSubsets(
self.flushWarnings(),
[{'category': category, 'message': message}])
self.assertEqual(self.flushWarnings(), [])
def test_unflushed(self):
"""
Any warnings emitted by a test which are not flushed are emitted to the
Python warning system.
"""
result = TestResult()
case = Mask.MockTests('test_unflushed')
case.run(result)
warningsShown = self.flushWarnings([Mask.MockTests.test_unflushed])
self.assertEqual(warningsShown[0]['message'], 'some warning text')
self.assertIdentical(warningsShown[0]['category'], UserWarning)
where = case.test_unflushed.im_func.func_code
filename = where.co_filename
# If someone edits MockTests.test_unflushed, the value added to
# firstlineno might need to change.
lineno = where.co_firstlineno + 4
self.assertEqual(warningsShown[0]['filename'], filename)
self.assertEqual(warningsShown[0]['lineno'], lineno)
self.assertEqual(len(warningsShown), 1)
def test_flushed(self):
"""
Any warnings emitted by a test which are flushed are not emitted to the
Python warning system.
"""
result = TestResult()
case = Mask.MockTests('test_flushed')
output = StringIO()
monkey = self.patch(sys, 'stdout', output)
case.run(result)
monkey.restore()
self.assertEqual(output.getvalue(), "")
def test_warningsConfiguredAsErrors(self):
"""
If a warnings filter has been installed which turns warnings into
exceptions, tests have an error added to the reporter for them for each
unflushed warning.
"""
class CustomWarning(Warning):
pass
result = TestResult()
case = Mask.MockTests('test_unflushed')
case.category = CustomWarning
originalWarnings = warnings.filters[:]
try:
warnings.simplefilter('error')
case.run(result)
self.assertEqual(len(result.errors), 1)
self.assertIdentical(result.errors[0][0], case)
result.errors[0][1].trap(CustomWarning)
finally:
warnings.filters[:] = originalWarnings
def test_flushedWarningsConfiguredAsErrors(self):
"""
If a warnings filter has been installed which turns warnings into
exceptions, tests which emit those warnings but flush them do not have
an error added to the reporter.
"""
class CustomWarning(Warning):
pass
result = TestResult()
case = Mask.MockTests('test_flushed')
case.category = CustomWarning
originalWarnings = warnings.filters[:]
try:
warnings.simplefilter('error')
case.run(result)
self.assertEqual(result.errors, [])
finally:
warnings.filters[:] = originalWarnings
def test_multipleFlushes(self):
"""
Any warnings emitted after a call to L{TestCase.flushWarnings} can be
flushed by another call to L{TestCase.flushWarnings}.
"""
warnings.warn("first message")
self.assertEqual(len(self.flushWarnings()), 1)
warnings.warn("second message")
self.assertEqual(len(self.flushWarnings()), 1)
def test_filterOnOffendingFunction(self):
"""
The list returned by L{TestCase.flushWarnings} includes only those
warnings which refer to the source of the function passed as the value
for C{offendingFunction}, if a value is passed for that parameter.
"""
firstMessage = "first warning text"
firstCategory = UserWarning
def one():
warnings.warn(firstMessage, firstCategory, stacklevel=1)
secondMessage = "some text"
secondCategory = RuntimeWarning
def two():
warnings.warn(secondMessage, secondCategory, stacklevel=1)
one()
two()
self.assertDictSubsets(
self.flushWarnings(offendingFunctions=[one]),
[{'category': firstCategory, 'message': firstMessage}])
self.assertDictSubsets(
self.flushWarnings(offendingFunctions=[two]),
[{'category': secondCategory, 'message': secondMessage}])
def test_functionBoundaries(self):
"""
Verify that warnings emitted at the very edges of a function are still
determined to be emitted from that function.
"""
def warner():
warnings.warn("first line warning")
warnings.warn("internal line warning")
warnings.warn("last line warning")
warner()
self.assertEqual(
len(self.flushWarnings(offendingFunctions=[warner])), 3)
def test_invalidFilter(self):
"""
If an object which is neither a function nor a method is included in
the C{offendingFunctions} list, L{TestCase.flushWarnings} raises
L{ValueError}. Such a call flushes no warnings.
"""
warnings.warn("oh no")
self.assertRaises(ValueError, self.flushWarnings, [None])
self.assertEqual(len(self.flushWarnings()), 1)
def test_missingSource(self):
"""
Warnings emitted by a function the source code of which is not
available can still be flushed.
"""
package = FilePath(self.mktemp()).child('twisted_private_helper')
package.makedirs()
package.child('__init__.py').setContent('')
package.child('missingsourcefile.py').setContent('''
import warnings
def foo():
warnings.warn("oh no")
''')
sys.path.insert(0, package.parent().path)
self.addCleanup(sys.path.remove, package.parent().path)
from twisted_private_helper import missingsourcefile
self.addCleanup(sys.modules.pop, 'twisted_private_helper')
self.addCleanup(sys.modules.pop, missingsourcefile.__name__)
package.child('missingsourcefile.py').remove()
missingsourcefile.foo()
self.assertEqual(len(self.flushWarnings([missingsourcefile.foo])), 1)
def test_renamedSource(self):
"""
Warnings emitted by a function defined in a file which has been renamed
since it was initially compiled can still be flushed.
This is testing the code which specifically supports working around the
unfortunate behavior of CPython to write a .py source file name into
the .pyc files it generates and then trust that it is correct in
various places. If source files are renamed, .pyc files may not be
regenerated, but they will contain incorrect filenames.
"""
package = FilePath(self.mktemp()).child('twisted_private_helper')
package.makedirs()
package.child('__init__.py').setContent('')
package.child('module.py').setContent('''
import warnings
def foo():
warnings.warn("oh no")
''')
sys.path.insert(0, package.parent().path)
self.addCleanup(sys.path.remove, package.parent().path)
# Import it to cause pycs to be generated
from twisted_private_helper import module
# Clean up the state resulting from that import; we're not going to use
# this module, so it should go away.
del sys.modules['twisted_private_helper']
del sys.modules[module.__name__]
# Rename the source directory
package.moveTo(package.sibling('twisted_renamed_helper'))
# Import the newly renamed version
from twisted_renamed_helper import module
self.addCleanup(sys.modules.pop, 'twisted_renamed_helper')
self.addCleanup(sys.modules.pop, module.__name__)
# Generate the warning
module.foo()
# Flush it
self.assertEqual(len(self.flushWarnings([module.foo])), 1)
class FakeWarning(Warning):
pass
class CollectWarningsTests(TestCase):
"""
Tests for L{_collectWarnings}.
"""
def test_callsObserver(self):
"""
L{_collectWarnings} calls the observer with each emitted warning.
"""
firstMessage = "dummy calls observer warning"
secondMessage = firstMessage[::-1]
events = []
def f():
events.append('call')
warnings.warn(firstMessage)
warnings.warn(secondMessage)
events.append('returning')
_collectWarnings(events.append, f)
self.assertEqual(events[0], 'call')
self.assertEqual(events[1].message, firstMessage)
self.assertEqual(events[2].message, secondMessage)
self.assertEqual(events[3], 'returning')
self.assertEqual(len(events), 4)
def test_suppresses(self):
"""
Any warnings emitted by a call to a function passed to
L{_collectWarnings} are not actually emitted to the warning system.
"""
output = StringIO()
self.patch(sys, 'stdout', output)
_collectWarnings(lambda x: None, warnings.warn, "text")
self.assertEqual(output.getvalue(), "")
def test_callsFunction(self):
"""
L{_collectWarnings} returns the result of calling the callable passed to
it with the parameters given.
"""
arguments = []
value = object()
def f(*args, **kwargs):
arguments.append((args, kwargs))
return value
result = _collectWarnings(lambda x: None, f, 1, 'a', b=2, c='d')
self.assertEqual(arguments, [((1, 'a'), {'b': 2, 'c': 'd'})])
self.assertIdentical(result, value)
def test_duplicateWarningCollected(self):
"""
Subsequent emissions of a warning from a particular source site can be
collected by L{_collectWarnings}. In particular, the per-module
emitted-warning cache should be bypassed (I{__warningregistry__}).
"""
# Make sure the worst case is tested: if __warningregistry__ isn't in a
# module's globals, then the warning system will add it and start using
# it to avoid emitting duplicate warnings. Delete __warningregistry__
# to ensure that even modules which are first imported as a test is
# running still interact properly with the warning system.
global __warningregistry__
del __warningregistry__
def f():
warnings.warn("foo")
warnings.simplefilter('default')
f()
events = []
_collectWarnings(events.append, f)
self.assertEqual(len(events), 1)
self.assertEqual(events[0].message, "foo")
self.assertEqual(len(self.flushWarnings()), 1)
def test_immutableObject(self):
"""
L{_collectWarnings}'s behavior is not altered by the presence of an
object which cannot have attributes set on it as a value in
C{sys.modules}.
"""
key = object()
sys.modules[key] = key
self.addCleanup(sys.modules.pop, key)
self.test_duplicateWarningCollected()
