Fixed bug 1726, with a test case.

Refactored tests for easier readability.

Prefix.py

@@ -0,0 +1,47 @@
+##############################################################################
+#
+# Copyright (c) 2001, 2002 Zope Corporation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE
+#
+##############################################################################
+"""ZODB undo support for Zope2.
+
+This package is used to support the Prefix object that Zope uses for
+undo.  It is a separate package only to aid configuration management.
+This package is included in Zope and ZODB3, so that ZODB3 is suitable
+for running a ZEO server that handles Zope undo.
+"""
+
+class Prefix:
+    """A Prefix() is equal to any path it is a prefix of.
+
+
+    This class can be compared to a string.
+    The comparison will return True if all path elements of the
+    Prefix are found at the beginning of the string being compared.
+
+    Two Prefixes can not be compared.
+    """
+
+    __no_side_effects__ = 1
+
+    def __init__(self, path):
+        path_list = path.split('/')
+        self.length = len(path_list)
+        self.path = path_list
+
+    def __cmp__(self, o):
+        other_path = o.split('/')
+        return cmp(other_path[:self.length], self.path)
+
+    def __repr__(self):
+        # makes failing tests easier to read
+        return "Prefix('%s')" % '/'.join(self.path)
+

tests/testPrefix.py

@@ -0,0 +1,32 @@
+##############################################################################
+#
+# Copyright (c) 2001, 2002 Zope Corporation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE
+#
+##############################################################################
+from ZopeUndo.Prefix import Prefix
+
+import unittest
+
+class PrefixTest(unittest.TestCase):
+
+    def test(self):
+        p1 = Prefix("/a/b")
+        for equal in ("/a/b", "/a/b/c", "/a/b/c/d"):
+            self.assertEqual(p1, equal)
+        for notEqual in ("", "/a/c", "/a/bbb", "///"):
+            self.assertNotEqual(p1, notEqual)
+
+        p2 = Prefix("")
+        for equal in ("", "/", "/def", "/a/b", "/a/b/c", "/a/b/c/d"):
+            self.assertEqual(p2, equal)
+
+def test_suite():
+    return unittest.makeSuite(PrefixTest)