From b5673a5176a561df34e066725bcfc9179d9d1522 Mon Sep 17 00:00:00 2001
From: Bryan Worrell <bworrell@mitre.org>
Date: Sun, 7 Jun 2015 12:40:36 -0400
Subject: [PATCH] Added unit test for #254 and isolate() and isolation()
 decorators and context managers.

---
 cybox/test/__init__.py                      | 85 +++++++++++++++++++++
 cybox/test/common/object_properties_test.py | 10 ++-
 2 files changed, 94 insertions(+), 1 deletion(-)

diff --git a/cybox/test/__init__.py b/cybox/test/__init__.py
index 641221c9..3057f9ca 100644
--- a/cybox/test/__init__.py
+++ b/cybox/test/__init__.py
@@ -1,9 +1,12 @@
 # Copyright (c) 2015, The MITRE Corporation. All rights reserved.
 # See LICENSE.txt for complete terms.
 
+import sys
 import json
 import logging
 import unittest
+import functools
+import contextlib
 
 from mixbox.binding_utils import ExternalEncoding
 from mixbox.vendor import six
@@ -14,6 +17,88 @@
 logger = logging.getLogger(__name__)
 
 
+@contextlib.contextmanager
+def isolation():
+    """Context manager that attempts to reset the sys.modules and globals()
+    to its initial state.
+
+    This helps eliminate issues where tests pass because of residuals caused
+    by previous imports.
+
+    Any code which leverages this context manager will need to re-import all
+    dependencies within.
+    """
+    def del_sys_modules(to_del):
+        for mod in to_del:
+            del sys.modules[mod]
+
+    def del_globals(to_del):
+        for g in globals_to_del:
+            del globals()[g]
+
+    mods_snapshot    = sys.modules.copy()
+    globals_snapshot = globals().copy()
+
+    required_mods    = ('unittest', 'logging', 'contextlib', 'json', 'six',
+                        'inspect', 'functools', 'sys')
+
+    required_globals = ('__builtins__', '__name__', '__doc__', '__package__',
+                        '__loader__', '__spec__')
+
+    # Removing parent test packages will raise a warning when importing within
+    # the context manager.
+    test_mods        = tuple(m for m in sys.modules if m.startswith('cybox.test'))
+
+    # Modules we want to keep in the sys.modules
+    mods_to_keep     = sys.builtin_module_names + test_mods + required_mods
+
+    # Globals we want to keep in globals()
+    globals_to_keep  = mods_to_keep + required_globals
+
+    # Globals and modules we want to remove.
+    mods_to_del      = (m for m in mods_snapshot if not m in mods_to_keep)
+    globals_to_del   = (g for g in globals_snapshot if g not in globals_to_keep)
+
+    try:
+        # Remove sys.modules and globals entries that are not required for
+        # the unit test.
+        del_sys_modules(mods_to_del)
+        del_globals(globals_to_del)
+
+        # Return to caller
+        yield
+
+    finally:
+        # Reset everything to the way it was.
+        mods_to_del     = [m for m in sys.modules if m not in mods_snapshot]
+        globals_to_del  = [g for g in globals() if g not in globals_snapshot]
+
+        # Remove any imports that may have occurred inside the context manager.
+        del_sys_modules(mods_to_del)
+        del_globals(globals_to_del)
+
+        # Reset everything to the way it was..sorta
+        sys.modules.update(mods_snapshot)
+        globals().update(globals_snapshot)
+
+
+def isolate(func):
+    """Decorator which leverages the ``isolation`` contextmanager to make the
+    decorated function unaware of outside imports or globals.
+
+    The globals() and sys.modules are returned to their previous state once
+    the decorated function exits.
+
+    This helps test units that should fail but pass due to residuals from
+    previous imports.
+    """
+    @functools.wraps(func)
+    def inner(*args, **kwargs):
+        with isolation():
+            return func(*args, **kwargs)
+    return inner
+
+
 def assert_equal_ignore(item1, item2, ignore_keys=None):
     """Recursively compare two dictionaries, ignoring differences in some keys.
     """
diff --git a/cybox/test/common/object_properties_test.py b/cybox/test/common/object_properties_test.py
index 48589843..6dd3b694 100644
--- a/cybox/test/common/object_properties_test.py
+++ b/cybox/test/common/object_properties_test.py
@@ -7,7 +7,7 @@
 
 from cybox.common import ObjectProperties, Property
 from cybox.objects.address_object import Address
-from cybox.test import EntityTestCase
+from cybox.test import EntityTestCase, isolate
 
 
 class TestProperty(EntityTestCase, unittest.TestCase):
@@ -48,5 +48,13 @@ def test_detect_address(self):
         self.assertTrue(isinstance(obj, Address))
 
 
+    @isolate
+    def test_parent(self):
+        """Test that the ``parent`` property of an ObjectProperties object
+        does not raise an AttributeError.
+        """
+        from cybox.objects.address_object import Address
+        self.assertTrue(bool(Address().parent.id_))
+
 if __name__ == "__main__":
     unittest.main()