- fix bug that made it possible for DemoStorage to hand out the same OID

  twice (with test)
- remove irrelevent and unused test_suite definition from testDemoStorage.py

src/ZODB/DemoStorage.py

@@ -176,9 +176,15 @@ class DemoStorage(object):
         except ZODB.POSException.POSKeyError:
             return self.base.loadSerial(oid, serial)
 
+    _issued_oids = {}
+
     def new_oid(self):
         while 1:
             oid = ZODB.utils.p64(random.randint(1, 9223372036854775807))
+
+            if oid in self._issued_oids:
+                continue
+
             try:
                 self.changes.load(oid, '')
             except ZODB.POSException.POSKeyError:
@@ -192,6 +198,7 @@ class DemoStorage(object):
             else:
                 continue
             
+            self._issued_oids[oid] = None
             return oid
 
     def pack(self, t, referencesf, gc=None):
@@ -222,6 +229,11 @@ class DemoStorage(object):
     def store(self, oid, serial, data, version, transaction):
         assert version=='', "versions aren't supported"
 
+        # Since the OID is being used, we don't have to keep up with it any
+        # more.
+        if oid in self._issued_oids:
+            del self._issued_oids[oid]
+
         # See if we already have changes for this oid
         try:
             old = self.changes.load(oid, '')[1]
@@ -239,6 +251,12 @@ class DemoStorage(object):
 
     def storeBlob(self, oid, oldserial, data, blobfilename, version,
                   transaction):
+
+        # Since the OID is being used, we don't have to keep up with it any
+        # more.
+        if oid in self._issued_oids:
+            del self._issued_oids[oid]
+
         try:
             return self.changes.storeBlob(
                 oid, oldserial, data, blobfilename, version, transaction)

src/ZODB/DemoStorage.test

@@ -327,3 +327,50 @@ and base options:
     'base.fs'
 
     >>> storage.close()
+
+
+Generating OIDs
+===============
+
+When asked for a new OID DemoStorage randomly chooses a value and then verifies
+that neither the base or changes storages already contain that OID.
+
+Under rare circumstances an OID can be chosen that has already been handed out,
+but which hasn't yet been comitted.  Lets verify that if the same OID is chosen
+twice during a transaction that everything will still work.
+
+First we'll get a single OID.
+
+    >>> import random
+    >>> storage = DemoStorage.push(storage)
+    >>> random.seed(47)
+    >>> storage.new_oid()
+    '\x10\x01\xa6bZ\x12\x98\xa2'
+
+Then we'll force the random number generator to use the same seed for the
+subsequent call to "new_oid" and show that we get a different OID.
+
+    >>> random.seed(47)
+    >>> oid = storage.new_oid()
+    >>> oid
+    'A\xe6\xcb\x06W\xed\xa2\x15'
+
+DemoStorage keeps up with the issued OIDs to know when not to reissue them...
+
+    >>> oid in storage._issued_oids
+    True
+
+...but once data is stored with a given OID...
+
+    >>> t = transaction.begin()
+    >>> storage.tpc_begin(t)
+    >>> tid = storage.store(oid, 0, 'data', '', t)
+
+...there's no need to remember it any longer:
+
+    >>> oid in storage._issued_oids
+    False
+
+We're done with the storage, so "unwrap" the underlying storage.
+
+    >>> storage = storage.pop()

src/ZODB/tests/testDemoStorage.py

@@ -156,20 +156,6 @@ def testSomeDelegation():
 
     """
 
-def test_suite():
-    return unittest.TestSuite((
-        doctest.DocFileSuite('synchronized.txt'),
-        doctest.DocTestSuite(
-            setUp=setUp, tearDown=ZODB.tests.util.tearDown,
-            ),
-        doctest.DocFileSuite(
-            'README.txt',
-            setUp=setUp, tearDown=ZODB.tests.util.tearDown,
-            ),
-        ))
-
-
-
 
 def test_suite():
     suite = unittest.TestSuite((