Add automated sys.stdout check.

tests/super_mox.py

 #!/usr/bin/python
 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Simplify unit tests based on pymox."""
 
 import __builtin__
 import os
 import random
 import shutil
 import string
+import StringIO
 import subprocess
 import sys
 
 sys.path.append(os.path.dirname(os.path.dirname(__file__)))
 from third_party.pymox import mox
 
 
 class IsOneOf(mox.Comparator):
   def __init__(self, keys):
     self._keys = keys
@@ skipping 56 matching lines @@
 
   def setUp(self):
     self.root_dir = self.Dir()
     self.args = self.Args()
     self.relpath = self.String(200)
 
   def tearDown(self):
     pass
 
 
-class SuperMoxTestBase(TestCaseUtils, mox.MoxTestBase):
+class StdoutCheck(object):
+  def setUp(self):
+    # Override the mock with a StringIO, it's much less painful to test.
+    self._old_stdout = sys.stdout
+    sys.stdout = StringIO.StringIO()
+    sys.stdout.flush = lambda: None
+
+  def tearDown(self):
+    try:
+      # If sys.stdout was used, self.checkstdout() must be called.
+      self.assertEquals('', sys.stdout.getvalue())
+    except AttributeError:
+      pass
+    sys.stdout = self._old_stdout
+
+  def checkstdout(self, expected):
+    value = sys.stdout.getvalue()
+    sys.stdout.close()
+    self.assertEquals(expected, value)
+
+
+class SuperMoxTestBase(TestCaseUtils, StdoutCheck, mox.MoxTestBase):
   def setUp(self):
     """Patch a few functions with know side-effects."""
     TestCaseUtils.setUp(self)
     mox.MoxTestBase.setUp(self)
     #self.mox.StubOutWithMock(__builtin__, 'open')
     os_to_mock = ('chdir', 'chown', 'close', 'closerange', 'dup', 'dup2',
       'fchdir', 'fchmod', 'fchown', 'fdopen', 'getcwd', 'getpid', 'lseek',
       'makedirs', 'mkdir', 'open', 'popen', 'popen2', 'popen3', 'popen4',
       'read', 'remove', 'removedirs', 'rename', 'renames', 'rmdir', 'symlink',
       'system', 'tmpfile', 'walk', 'write')
     self.MockList(os, os_to_mock)
     os_path_to_mock = ('abspath', 'exists', 'getsize', 'isdir', 'isfile',
       'islink', 'ismount', 'lexists', 'realpath', 'samefile', 'walk')
     self.MockList(os.path, os_path_to_mock)
     self.MockList(shutil, ('rmtree'))
     self.MockList(subprocess, ('call', 'Popen'))
     # Don't mock stderr since it confuses unittests.
-    self.MockList(sys, ('stdin', 'stdout'))
+    self.MockList(sys, ('stdin'))
+    StdoutCheck.setUp(self)
 
   def tearDown(self):
+    StdoutCheck.tearDown(self)
     TestCaseUtils.tearDown(self)
     mox.MoxTestBase.tearDown(self)
 
   def MockList(self, parent, items_to_mock):
     for item in items_to_mock:
       # Skip over items not present because of OS-specific implementation,
       # implemented only in later python version, etc.
       if hasattr(parent, item):
         try:
           self.mox.StubOutWithMock(parent, item)
         except TypeError:
           raise TypeError('Couldn\'t mock %s in %s' % (item, parent.__name__))
 
   def UnMock(self, object, name):
     """Restore an object inside a test."""
     for (parent, old_child, child_name) in self.mox.stubs.cache:
       if parent == object and child_name == name:
         setattr(parent, child_name, old_child)
         break