From 0351c33996da073395f5af405f3cb36d800839ac Mon Sep 17 00:00:00 2001
From: smiddlek <smiddlek@b1010a0a-674b-0410-b734-77272b80c875>
Date: Wed, 7 Jul 2010 17:48:13 +0000
Subject: Add an Is() comparator for checking identity, instead of equality.
 By: vmalloc

git-svn-id: http://pymox.googlecode.com/svn/trunk@53 b1010a0a-674b-0410-b734-77272b80c875
---
 mox.py      |  7 +++++++
 mox_test.py | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/mox.py b/mox.py
index 948973a..c8ef6a6 100755
--- a/mox.py
+++ b/mox.py
@@ -1237,6 +1237,13 @@ class Comparator:
   def __ne__(self, rhs):
     return not self.equals(rhs)
 
+class Is(Comparator):
+  def __init__(self, obj):
+    self._obj = obj
+  def equals(self, rhs):
+    return rhs is self._obj
+  def __repr__(self):
+    return "<is %r (%s)>" % (self._obj, id(self._obj))
 
 class IsA(Comparator):
   """This class wraps a basic Python type or class.  It is used to verify
diff --git a/mox_test.py b/mox_test.py
index 005455a..2166107 100755
--- a/mox_test.py
+++ b/mox_test.py
@@ -259,6 +259,52 @@ class RegexTest(unittest.TestCase):
                  "<regular expression 'a\s+b', flags=4>")
 
 
+class IsTest(unittest.TestCase):
+  """Verify Is correctly checks equality based upon identity, not value"""
+
+  class AlwaysComparesTrue(object):
+    def __eq__(self, other):
+      return True
+    def __cmp__(self, other):
+      return 0
+    def __ne__(self, other):
+      return False
+
+  def testEqualityValid(self):
+    o1 = self.AlwaysComparesTrue()
+    self.assertTrue(mox.Is(o1), o1)
+
+  def testEqualityInvalid(self):
+    o1 = self.AlwaysComparesTrue()
+    o2 = self.AlwaysComparesTrue()
+    self.assertTrue(o1 == o2)
+    # but...
+    self.assertFalse(mox.Is(o1) == o2)
+
+  def testInequalityValid(self):
+    o1 = self.AlwaysComparesTrue()
+    o2 = self.AlwaysComparesTrue()
+    self.assertTrue(mox.Is(o1) != o2)
+
+  def testInequalityInvalid(self):
+    o1 = self.AlwaysComparesTrue()
+    self.assertFalse(mox.Is(o1) != o1)
+
+  def testEqualityInListValid(self):
+    o1 = self.AlwaysComparesTrue()
+    o2 = self.AlwaysComparesTrue()
+    isa_list = [mox.Is(o1), mox.Is(o2)]
+    str_list = [o1, o2]
+    self.assertTrue(isa_list == str_list)
+
+  def testEquailtyInListInvalid(self):
+    o1 = self.AlwaysComparesTrue()
+    o2 = self.AlwaysComparesTrue()
+    isa_list = [mox.Is(o1), mox.Is(o2)]
+    mixed_list = [o2, o1]
+    self.assertFalse(isa_list == mixed_list)
+
+
 class IsATest(unittest.TestCase):
   """Verify IsA correctly checks equality based upon class type, not value."""
 
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