Add some simple tests of subtransactions.

src/ZODB/tests/testSubTransaction.py

+##############################################################################
+#
+# Copyright (c) 2004 Zope Corporation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.0 (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.
+#
+##############################################################################
+r"""
+ZODB subtransaction tests
+=========================
+
+Subtransactions are provided by a generic transaction interface, but
+only supported by ZODB.  These tests verify that some of the important
+cases work as expected.
+
+>>> import transaction
+>>> from ZODB import DB
+>>> from ZODB.tests.test_storage import MinimalMemoryStorage
+>>> from ZODB.tests.MinPO import MinPO
+
+First create a few objects in the database root with a normal commit.
+We're going to make a series of modifications to these objects.
+
+>>> db = DB(MinimalMemoryStorage())
+>>> cn = db.open()
+>>> rt = cn.root()
+>>> def init():
+...     global a, b, c
+...     a = rt["a"] = MinPO("a0")
+...     b = rt["b"] = MinPO("b0")
+...     c = rt["c"] = MinPO("c0")
+...     transaction.commit()
+>>> init()
+
+We'll also open a second database connection and use it to verify that
+the intermediate results of subtransactions are not visible to other
+connections.
+
+>>> cn2 = db.open(synch=False)
+>>> rt2 = cn2.root()
+>>> shadow_a = rt2["a"]
+>>> shadow_b = rt2["b"]
+>>> shadow_c = rt2["c"]
+
+Subtransaction commit
+---------------------
+
+We'll make a series of modifications in subtransactions.
+
+>>> a.value = "a1"
+>>> b.value = "b1"
+>>> transaction.commit(1)
+>>> a.value, b.value
+('a1', 'b1')
+>>> shadow_a.value, shadow_b.value
+('a0', 'b0')
+
+>>> a.value = "a2"
+>>> c.value = "c1"
+>>> transaction.commit(1)
+>>> a.value, c.value
+('a2', 'c1')
+>>> shadow_a.value, shadow_c.value
+('a0', 'c0')
+
+>>> a.value = "a3"
+>>> transaction.commit(1)
+>>> a.value
+'a3'
+>>> shadow_a.value
+'a0'
+
+>>> transaction.commit()
+
+>>> a.value, b.value, c.value
+('a3', 'b1', 'c1')
+
+Subtransaction with nested abort
+--------------------------------
+
+>>> init()
+>>> a.value = "a1"
+>>> transaction.commit(1)
+
+>>> b.value = "b1"
+>>> transaction.commit(1)
+
+A sub-transaction abort will undo current changes, reverting to the
+database state as of the last sub-transaction commit.  There is
+(apparently) no way to abort an already-committed subtransaction.
+
+>>> c.value = "c1"
+>>> transaction.abort(1)
+
+Multiple aborts have no extra effect.
+
+>>> transaction.abort(1)
+
+>>> a.value, b.value, c.value
+('a1', 'b1', 'c0')
+
+>>> transaction.commit()
+>>> a.value, b.value, c.value
+('a1', 'b1', 'c0')
+
+Subtransaction with top-level abort
+-----------------------------------
+
+>>> init()
+>>> a.value = "a1"
+>>> transaction.commit(1)
+
+>>> b.value = "b1"
+>>> transaction.commit(1)
+
+A sub-transaction abort will undo current changes, reverting to the
+database state as of the last sub-transaction commit.  There is
+(apparently) no way to abort an already-committed subtransaction.
+
+>>> c.value = "c1"
+>>> transaction.abort(1)
+
+>>> transaction.abort()
+>>> a.value, b.value, c.value
+('a0', 'b0', 'c0')
+
+"""
+
+import doctest
+
+def test_suite():
+    return doctest.DocTestSuite()