Reach 100% coverage.

.coveragerc

@@ -0,0 +1,9 @@
+[run]
+source = zope.keyreference
+
+[report]
+exclude_lines =
+    pragma: no cover
+    if __name__ == '__main__':
+    raise NotImplementedError
+    raise AssertionError

src/zope/keyreference/interfaces.py

@@ -27,17 +27,19 @@ class NotYet(Exception):
     (e.g. at the end of the transaction).
     """
 
+
 class IKeyReference(zope.interface.Interface):
     """A reference to an object (similar to a weak reference).
 
     The references are compared by their hashes.
     """
 
-    key_type_id = DottedName(title=_('Key Type Id'),
+    key_type_id = DottedName(
+        title=_('Key Type Id'),
         description=_('Key references should sort first '
-            'on their key type and second on any type-specific '
-            'information.')
-        )
+                      'on their key type and second on any type-specific '
+                      'information.')
+    )
 
     def __call__():
         """Get the object this reference is linking to.
@@ -54,19 +56,19 @@ def __cmp__(ref):
         """
 
     def __eq__(ref):
-        pass
+        "KeyReferences must be totally orderable."
 
     def __lt__(ref):
-        pass
+        "KeyReferences must be totally orderable."
 
     def __ne__(ref):
-        pass
+        "KeyReferences must be totally orderable."
 
     def __gt__(ref):
-        pass
+        "KeyReferences must be totally orderable."
 
     def __le__(ref):
-        pass
+        "KeyReferences must be totally orderable."
 
     def __ge__(ref):
-        pass
+        "KeyReferences must be totally orderable."

src/zope/keyreference/persistent.py

@@ -96,8 +96,16 @@ def _get_cmp_keys(self, other):
         return self.key_type_id, other.key_type_id
 
     # Py3: For Python 2 BBB.
+    # If we implement all the rich comparison operations, though, this is
+    # never actually called.
     def __cmp__(self, other):
-        return cmp(*self._get_cmp_keys(other))
+        my_keys, other_keys = self._get_cmp_keys(other)
+        if my_keys == other_keys:
+            return 0
+        if my_keys > other_keys:
+            return 1
+        return -1
+
 
     def __eq__(self, other):
         a, b = self._get_cmp_keys(other)

src/zope/keyreference/testing.py

@@ -11,16 +11,20 @@
 # FOR A PARTICULAR PURPOSE.
 #
 ##############################################################################
-"""Testing components
 """
+Testing components.
+"""
+
 import zope.interface
 import zope.component
 import zope.keyreference.interfaces
 
 @zope.component.adapter(zope.interface.Interface)
 @zope.interface.implementer(zope.keyreference.interfaces.IKeyReference)
 class SimpleKeyReference(object):
-    """An IReference for all objects. This implementation is *not* ZODB safe.
+    """An IReference for all objects. This implementation is *not*
+    ZODB safe.
+
     """
 
     key_type_id = 'zope.app.keyreference.simple'
@@ -41,8 +45,15 @@ def _get_cmp_keys(self, other):
         return self.key_type_id, other.key_type_id
 
     # Py3: For Python 2 BBB.
+    # If we implement all the rich comparison operations, though, this is
+    # never actually called.
     def __cmp__(self, other):
-        return cmp(*self._get_cmp_keys(other))
+        my_keys, other_keys = self._get_cmp_keys(other)
+        if my_keys == other_keys:
+            return 0
+        if my_keys > other_keys:
+            return 1
+        return -1
 
     def __eq__(self, other):
         a, b = self._get_cmp_keys(other)

src/zope/keyreference/tests.py

@@ -18,6 +18,80 @@
 import unittest
 from zope.testing import renormalizing
 
+
+class MockDatabase(object):
+    database_name = ''
+
+
+class MockJar(object):
+
+    def __init__(self):
+        self._db = MockDatabase()
+
+    def db(self):
+        return self._db
+
+
+class MockPersistent(object):
+    _p_oid = 1
+    _p_jar = MockJar()
+
+    def __hash__(self):
+        # SimpleKeyReference depends on hash
+        return hash(self._p_oid)
+
+
+class TestKeyReferenceToPersistent(unittest.TestCase):
+
+    def makeOne(self, obj):
+        from zope.keyreference.persistent import KeyReferenceToPersistent
+        return KeyReferenceToPersistent(obj)
+
+    def test__cmp__(self):
+
+        persistent = MockPersistent()
+
+        eq1 = self.makeOne(persistent)
+        eq2 = self.makeOne(persistent)
+
+        self.assertEqual(eq1, eq2)
+        self.assertEqual(0, eq1.__cmp__(eq2))
+        self.assertEqual(0, eq1.__cmp__(eq1))
+        self.assertEqual(0, eq2.__cmp__(eq1))
+
+        # But if they have different key_type_id, they
+        # only compare based on that.
+        eq2.key_type_id = 'aaa'
+        self.assertNotEqual(eq1, eq2)
+
+        persistent_gt = MockPersistent()
+        persistent_gt._p_oid = 2
+
+        gt = self.makeOne(persistent_gt)
+        __traceback_info__ = hash(gt), hash(eq1), hash(persistent._p_oid)
+        self.assertGreater(gt, eq1)
+        self.assertGreaterEqual(gt, eq1)
+        self.assertNotEqual(gt, eq1)
+        self.assertEqual(1, gt.__cmp__(eq1))
+
+        self.assertLess(eq1, gt)
+        self.assertLessEqual(eq1, gt)
+        self.assertEqual(-1, eq1.__cmp__(gt))
+
+
+    def test__call__(self):
+        persistent = MockPersistent()
+        obj = self.makeOne(persistent)
+
+        self.assertIs(persistent, obj())
+
+class TestSimpleKeyReference(TestKeyReferenceToPersistent):
+
+    def makeOne(self, obj):
+        from zope.keyreference.testing import SimpleKeyReference
+        return SimpleKeyReference(obj)
+
+
 checker = renormalizing.RENormalizing([
     # Python 3 adds module name to exceptions.
     (re.compile("zope.keyreference.interfaces.NotYet"),
@@ -61,8 +135,5 @@ def test_suite():
     return unittest.TestSuite((
         doctest.DocFileSuite('persistent.txt', checker=checker),
         doctest.DocTestSuite(),
-        ))
-
-if __name__ == '__main__':
-    unittest.main(defaultTest='test_suite')
-
+        unittest.defaultTestLoader.loadTestsFromName(__name__),
+    ))

tox.ini

@@ -20,7 +20,7 @@ basepython =
     python3.6
 commands =
     coverage run -m zope.testrunner --test-path=src []
-    coverage report --fail-under=67
+    coverage report --fail-under=100
 deps =
     {[testenv]deps}
     coverage