Twisted tests now pass under --debug-stacktraces

Our tests make assertions that only hold when debugging is disabled.
This patch updates the code to ensure that debugging is in the state
we want.

NEWS

@@ -12,6 +12,9 @@ Changes
 * Python 2.6 and 3.2 are no longer supported. If you want to use either of
   these versions of Python, use testtools 1.9.0. (Jonathan Lange)
 
+* Make ``fixtures`` a real dependency, not just a test dependency.
+  (Jonathan Lange)
+
 
 1.9.0
 ~~~~~

requirements.txt

@@ -1,9 +1,9 @@
 pbr>=0.11
 extras
+fixtures>=1.3.0
 pyrsistent
 # 'mimeparse' has not been uploaded by the maintainer with Python3 compat
 # but someone kindly uploaded a fixed version as 'python-mimeparse'.
 python-mimeparse
 unittest2>=1.0.0
 traceback2
-fixtures>=1.3.0

testtools/_deferreddebug.py

@@ -0,0 +1,21 @@
+# Copyright (c) testtools developers. See LICENSE for details.
+#
+# TODO: Move this to testtools.twistedsupport. See testing-cabal/testtools#202.
+
+from fixtures import Fixture, MonkeyPatch
+
+
+class DebugTwisted(Fixture):
+    """Set debug options for Twisted."""
+
+    def __init__(self, debug=True):
+        super(DebugTwisted, self).__init__()
+        self._debug_setting = debug
+
+    def _setUp(self):
+        self.useFixture(
+            MonkeyPatch('twisted.internet.defer.Deferred.debug',
+                        self._debug_setting))
+        self.useFixture(
+            MonkeyPatch('twisted.internet.base.DelayedCall.debug',
+                        self._debug_setting))

testtools/_spinner.py

@@ -16,12 +16,12 @@
     'trap_unhandled_errors',
     ]
 
+from fixtures import Fixture
 import signal
 
-from testtools.monkey import MonkeyPatcher
+from testtools._deferreddebug import DebugTwisted
 
 from twisted.internet import defer
-from twisted.internet.base import DelayedCall
 from twisted.internet.interfaces import IReactorThreads
 from twisted.python.failure import Failure
 from twisted.python.util import mergeFunctionMetadata
@@ -265,12 +265,12 @@ def run(self, timeout, function, *args, **kwargs):
         :return: Whatever is at the end of the function's callback chain.  If
             it's an error, then raise that.
         """
-        debug = MonkeyPatcher()
         if self._debug:
-            debug.add_patch(defer.Deferred, 'debug', True)
-            debug.add_patch(DelayedCall, 'debug', True)
-        debug.patch()
-        try:
+            debug_settings = DebugTwisted(True)
+        else:
+            debug_settings = Fixture()
+
+        with debug_settings:
             junk = self.get_junk()
             if junk:
                 raise StaleJunkError(junk)
@@ -300,5 +300,3 @@ def run_function():
                 return self._get_result()
             finally:
                 self._clean()
-        finally:
-            debug.restore()

testtools/tests/test_deferredruntest.py

@@ -12,6 +12,7 @@
     TestCase,
     TestResult,
     )
+from testtools._deferreddebug import DebugTwisted
 from testtools.matchers import (
     AfterPreprocessing,
     Contains,
@@ -388,6 +389,10 @@ def test_cruft(self):
     def test_unhandled_error_from_deferred(self):
         # If there's a Deferred with an unhandled error, the test fails.  Each
         # unhandled error is reported with a separate traceback.
+
+        # We're interested in the behavior when debugging is disabled. When
+        # debugging is enabled, we get more stack traces.
+        self.useFixture(DebugTwisted(False))
         class SomeCase(TestCase):
             def test_cruft(self):
                 # Note we aren't returning the Deferred so that the error will
@@ -415,6 +420,10 @@ def test_unhandled_error_from_deferred_combined_with_error(self):
         # If there's a Deferred with an unhandled error, the test fails.  Each
         # unhandled error is reported with a separate traceback, and the error
         # is still reported.
+
+        # We're interested in the behavior when debugging is disabled. When
+        # debugging is enabled, we get more stack traces.
+        self.useFixture(DebugTwisted(False))
         class SomeCase(TestCase):
             def test_cruft(self):
                 # Note we aren't returning the Deferred so that the error will
@@ -573,6 +582,10 @@ def test_something(self):
     def test_only_addError_once(self):
         # Even if the reactor is unclean and the test raises an error and the
         # cleanups raise errors, we only called addError once per test.
+
+        # We're interested in the behavior when debugging is disabled. When
+        # debugging is enabled, we get more stack traces.
+        self.useFixture(DebugTwisted(False))
         reactor = self.make_reactor()
         class WhenItRains(TestCase):
             def it_pours(self):