[tests] add u1db sync tests to soledad couch tests

3 files changed, 1020 insertions, 20 deletions

diff --git a/common/src/leap/soledad/common/tests/test_couch.py b/common/src/leap/soledad/common/tests/test_couch.py
index 48f0f51b..021888c1 100644
--- a/common/src/leap/soledad/common/tests/test_couch.py
+++ b/common/src/leap/soledad/common/tests/test_couch.py
@@ -21,20 +21,29 @@ Test ObjectStore and Couch backend bits.
 """
 
 
-import simplejson as json
+import json
 
 from urlparse import urljoin
-from u1db import errors as u1db_errors
 from couchdb.client import Server
 
 from testscenarios import TestWithScenarios
 
-from leap.soledad.common import couch, errors
+from u1db import errors as u1db_errors
+from u1db import SyncTarget
+from u1db import vectorclock
+
+from leap.soledad.common import couch
+from leap.soledad.common import errors
 
 from leap.soledad.common.tests import u1db_tests as tests
-from leap.soledad.common.tests.u1db_tests import test_backends
-from leap.soledad.common.tests.u1db_tests import test_sync
 from leap.soledad.common.tests.util import CouchDBTestCase
+from leap.soledad.common.tests.util import make_local_db_and_target
+from leap.soledad.common.tests.util import sync_via_synchronizer
+
+from leap.soledad.common.tests.u1db_tests import test_backends
+from leap.soledad.common.tests.u1db_tests import DatabaseBaseTests
+from leap.soledad.common.tests.u1db_tests import TestCaseWithServer
+
 from u1db.backends.inmemory import InMemoryIndex
 
 
@@ -218,7 +227,7 @@ class CouchWithConflictsTests(
 # -----------------------------------------------------------------------------
 
 target_scenarios = [
-    ('local', {'create_db_and_target': test_sync._make_local_db_and_target}), ]
+    ('local', {'create_db_and_target': make_local_db_and_target}), ]
 
 
 simple_doc = tests.simple_doc
@@ -226,10 +235,56 @@ nested_doc = tests.nested_doc
 
 
 class CouchDatabaseSyncTargetTests(
-        TestWithScenarios, test_sync.DatabaseSyncTargetTests, CouchDBTestCase):
+        TestWithScenarios,
+        DatabaseBaseTests,
+        TestCaseWithServer,
+        CouchDBTestCase):
+
+    # TODO: implement _set_trace_hook(_shallow) in CouchSyncTarget so
+    #       skipped tests can be succesfully executed.
+
+    # whitebox true means self.db is the actual local db object
+    # against which the sync is performed
+    whitebox = True
 
     scenarios = (tests.multiply_scenarios(COUCH_SCENARIOS, target_scenarios))
 
+    def set_trace_hook(self, callback, shallow=False):
+        setter = (self.st._set_trace_hook if not shallow else
+                  self.st._set_trace_hook_shallow)
+        try:
+            setter(callback)
+        except NotImplementedError:
+            self.skipTest("%s does not implement _set_trace_hook"
+                          % (self.st.__class__.__name__,))
+
+    def setUp(self):
+        CouchDBTestCase.setUp(self)
+        # from DatabaseBaseTests.setUp
+        self.db = self.create_database('test')
+        # from TestCaseWithServer.setUp
+        self.server = self.server_thread = self.port = None
+        # other stuff
+        self.db, self.st = self.create_db_and_target(self)
+        self.other_changes = []
+
+    def tearDown(self):
+        CouchDBTestCase.tearDown(self)
+        # from TestCaseWithServer.tearDown
+        if self.server is not None:
+            self.server.shutdown()
+            self.server_thread.join()
+            self.server.server_close()
+        if self.port:
+            self.port.stopListening()
+        # from DatabaseBaseTests.tearDown
+        if hasattr(self, 'db') and self.db is not None:
+            self.db.close()
+
+    def receive_doc(self, doc, gen, trans_id):
+        self.other_changes.append(
+            (doc.doc_id, doc.rev, doc.get_json(), gen, trans_id))
+
     def test_sync_exchange_returns_many_new_docs(self):
         # This test was replicated to allow dictionaries to be compared after
         # JSON expansion (because one dictionary may have many different
@@ -252,6 +307,268 @@ class CouchDatabaseSyncTargetTests(
                 {'last_gen': 2, 'docs':
                  [(doc.doc_id, doc.rev), (doc2.doc_id, doc2.rev)]})
 
+    def test_get_sync_target(self):
+        self.assertIsNot(None, self.st)
+
+    def test_get_sync_info(self):
+        self.assertEqual(
+            ('test', 0, '', 0, ''), self.st.get_sync_info('other'))
+
+    def test_create_doc_updates_sync_info(self):
+        self.assertEqual(
+            ('test', 0, '', 0, ''), self.st.get_sync_info('other'))
+        self.db.create_doc_from_json(simple_doc)
+        self.assertEqual(1, self.st.get_sync_info('other')[1])
+
+    def test_record_sync_info(self):
+        self.st.record_sync_info('replica', 10, 'T-transid')
+        self.assertEqual(
+            ('test', 0, '', 10, 'T-transid'), self.st.get_sync_info('replica'))
+
+    def test_sync_exchange(self):
+        docs_by_gen = [
+            (self.make_document('doc-id', 'replica:1', simple_doc), 10,
+             'T-sid')]
+        new_gen, trans_id = self.st.sync_exchange(
+            docs_by_gen, 'replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertGetDoc(self.db, 'doc-id', 'replica:1', simple_doc, False)
+        self.assertTransactionLog(['doc-id'], self.db)
+        last_trans_id = self.getLastTransId(self.db)
+        self.assertEqual(([], 1, last_trans_id),
+                         (self.other_changes, new_gen, last_trans_id))
+        self.assertEqual(10, self.st.get_sync_info('replica')[3])
+
+    def test_sync_exchange_deleted(self):
+        doc = self.db.create_doc_from_json('{}')
+        edit_rev = 'replica:1|' + doc.rev
+        docs_by_gen = [
+            (self.make_document(doc.doc_id, edit_rev, None), 10, 'T-sid')]
+        new_gen, trans_id = self.st.sync_exchange(
+            docs_by_gen, 'replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertGetDocIncludeDeleted(
+            self.db, doc.doc_id, edit_rev, None, False)
+        self.assertTransactionLog([doc.doc_id, doc.doc_id], self.db)
+        last_trans_id = self.getLastTransId(self.db)
+        self.assertEqual(([], 2, last_trans_id),
+                         (self.other_changes, new_gen, trans_id))
+        self.assertEqual(10, self.st.get_sync_info('replica')[3])
+
+    def test_sync_exchange_push_many(self):
+        docs_by_gen = [
+            (self.make_document('doc-id', 'replica:1', simple_doc), 10, 'T-1'),
+            (self.make_document('doc-id2', 'replica:1', nested_doc), 11,
+             'T-2')]
+        new_gen, trans_id = self.st.sync_exchange(
+            docs_by_gen, 'replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertGetDoc(self.db, 'doc-id', 'replica:1', simple_doc, False)
+        self.assertGetDoc(self.db, 'doc-id2', 'replica:1', nested_doc, False)
+        self.assertTransactionLog(['doc-id', 'doc-id2'], self.db)
+        last_trans_id = self.getLastTransId(self.db)
+        self.assertEqual(([], 2, last_trans_id),
+                         (self.other_changes, new_gen, trans_id))
+        self.assertEqual(11, self.st.get_sync_info('replica')[3])
+
+    def test_sync_exchange_refuses_conflicts(self):
+        doc = self.db.create_doc_from_json(simple_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        new_doc = '{"key": "altval"}'
+        docs_by_gen = [
+            (self.make_document(doc.doc_id, 'replica:1', new_doc), 10,
+             'T-sid')]
+        new_gen, _ = self.st.sync_exchange(
+            docs_by_gen, 'replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        self.assertEqual(
+            (doc.doc_id, doc.rev, simple_doc, 1), self.other_changes[0][:-1])
+        self.assertEqual(1, new_gen)
+        if self.whitebox:
+            self.assertEqual(self.db._last_exchange_log['return'],
+                             {'last_gen': 1, 'docs': [(doc.doc_id, doc.rev)]})
+
+    def test_sync_exchange_ignores_convergence(self):
+        doc = self.db.create_doc_from_json(simple_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        gen, txid = self.db._get_generation_info()
+        docs_by_gen = [
+            (self.make_document(doc.doc_id, doc.rev, simple_doc), 10, 'T-sid')]
+        new_gen, _ = self.st.sync_exchange(
+            docs_by_gen, 'replica', last_known_generation=gen,
+            last_known_trans_id=txid, return_doc_cb=self.receive_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        self.assertEqual(([], 1), (self.other_changes, new_gen))
+
+    def test_sync_exchange_returns_new_docs(self):
+        doc = self.db.create_doc_from_json(simple_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        new_gen, _ = self.st.sync_exchange(
+            [], 'other-replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        self.assertEqual(
+            (doc.doc_id, doc.rev, simple_doc, 1), self.other_changes[0][:-1])
+        self.assertEqual(1, new_gen)
+        if self.whitebox:
+            self.assertEqual(self.db._last_exchange_log['return'],
+                             {'last_gen': 1, 'docs': [(doc.doc_id, doc.rev)]})
+
+    def test_sync_exchange_returns_deleted_docs(self):
+        doc = self.db.create_doc_from_json(simple_doc)
+        self.db.delete_doc(doc)
+        self.assertTransactionLog([doc.doc_id, doc.doc_id], self.db)
+        new_gen, _ = self.st.sync_exchange(
+            [], 'other-replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertTransactionLog([doc.doc_id, doc.doc_id], self.db)
+        self.assertEqual(
+            (doc.doc_id, doc.rev, None, 2), self.other_changes[0][:-1])
+        self.assertEqual(2, new_gen)
+        if self.whitebox:
+            self.assertEqual(self.db._last_exchange_log['return'],
+                             {'last_gen': 2, 'docs': [(doc.doc_id, doc.rev)]})
+
+    def test_sync_exchange_getting_newer_docs(self):
+        doc = self.db.create_doc_from_json(simple_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        new_doc = '{"key": "altval"}'
+        docs_by_gen = [
+            (self.make_document(doc.doc_id, 'test:1|z:2', new_doc), 10,
+             'T-sid')]
+        new_gen, _ = self.st.sync_exchange(
+            docs_by_gen, 'other-replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertTransactionLog([doc.doc_id, doc.doc_id], self.db)
+        self.assertEqual(([], 2), (self.other_changes, new_gen))
+
+    def test_sync_exchange_with_concurrent_updates_of_synced_doc(self):
+        expected = []
+
+        def before_whatschanged_cb(state):
+            if state != 'before whats_changed':
+                return
+            cont = '{"key": "cuncurrent"}'
+            conc_rev = self.db.put_doc(
+                self.make_document(doc.doc_id, 'test:1|z:2', cont))
+            expected.append((doc.doc_id, conc_rev, cont, 3))
+
+        self.set_trace_hook(before_whatschanged_cb)
+        doc = self.db.create_doc_from_json(simple_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        new_doc = '{"key": "altval"}'
+        docs_by_gen = [
+            (self.make_document(doc.doc_id, 'test:1|z:2', new_doc), 10,
+             'T-sid')]
+        new_gen, _ = self.st.sync_exchange(
+            docs_by_gen, 'other-replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertEqual(expected, [c[:-1] for c in self.other_changes])
+        self.assertEqual(3, new_gen)
+
+    def test_sync_exchange_with_concurrent_updates(self):
+
+        def after_whatschanged_cb(state):
+            if state != 'after whats_changed':
+                return
+            self.db.create_doc_from_json('{"new": "doc"}')
+
+        self.set_trace_hook(after_whatschanged_cb)
+        doc = self.db.create_doc_from_json(simple_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        new_doc = '{"key": "altval"}'
+        docs_by_gen = [
+            (self.make_document(doc.doc_id, 'test:1|z:2', new_doc), 10,
+             'T-sid')]
+        new_gen, _ = self.st.sync_exchange(
+            docs_by_gen, 'other-replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertEqual(([], 2), (self.other_changes, new_gen))
+
+    def test_sync_exchange_converged_handling(self):
+        doc = self.db.create_doc_from_json(simple_doc)
+        docs_by_gen = [
+            (self.make_document('new', 'other:1', '{}'), 4, 'T-foo'),
+            (self.make_document(doc.doc_id, doc.rev, doc.get_json()), 5,
+             'T-bar')]
+        new_gen, _ = self.st.sync_exchange(
+            docs_by_gen, 'other-replica', last_known_generation=0,
+            last_known_trans_id=None, return_doc_cb=self.receive_doc)
+        self.assertEqual(([], 2), (self.other_changes, new_gen))
+
+    def test_sync_exchange_detect_incomplete_exchange(self):
+        def before_get_docs_explode(state):
+            if state != 'before get_docs':
+                return
+            raise u1db_errors.U1DBError("fail")
+        self.set_trace_hook(before_get_docs_explode)
+        # suppress traceback printing in the wsgiref server
+        # self.patch(simple_server.ServerHandler,
+        #           'log_exception', lambda h, exc_info: None)
+        doc = self.db.create_doc_from_json(simple_doc)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        self.assertRaises(
+            (u1db_errors.U1DBError, u1db_errors.BrokenSyncStream),
+            self.st.sync_exchange, [], 'other-replica',
+            last_known_generation=0, last_known_trans_id=None,
+            return_doc_cb=self.receive_doc)
+
+    def test_sync_exchange_doc_ids(self):
+        sync_exchange_doc_ids = getattr(self.st, 'sync_exchange_doc_ids', None)
+        if sync_exchange_doc_ids is None:
+            self.skipTest("sync_exchange_doc_ids not implemented")
+        db2 = self.create_database('test2')
+        doc = db2.create_doc_from_json(simple_doc)
+        new_gen, trans_id = sync_exchange_doc_ids(
+            db2, [(doc.doc_id, 10, 'T-sid')], 0, None,
+            return_doc_cb=self.receive_doc)
+        self.assertGetDoc(self.db, doc.doc_id, doc.rev, simple_doc, False)
+        self.assertTransactionLog([doc.doc_id], self.db)
+        last_trans_id = self.getLastTransId(self.db)
+        self.assertEqual(([], 1, last_trans_id),
+                         (self.other_changes, new_gen, trans_id))
+        self.assertEqual(10, self.st.get_sync_info(db2._replica_uid)[3])
+
+    def test__set_trace_hook(self):
+        called = []
+
+        def cb(state):
+            called.append(state)
+
+        self.set_trace_hook(cb)
+        self.st.sync_exchange([], 'replica', 0, None, self.receive_doc)
+        self.st.record_sync_info('replica', 0, 'T-sid')
+        self.assertEqual(['before whats_changed',
+                          'after whats_changed',
+                          'before get_docs',
+                          'record_sync_info',
+                          ],
+                         called)
+
+    def test__set_trace_hook_shallow(self):
+        if (self.st._set_trace_hook_shallow == self.st._set_trace_hook
+                or self.st._set_trace_hook_shallow.im_func ==
+                SyncTarget._set_trace_hook_shallow.im_func):
+            # shallow same as full
+            expected = ['before whats_changed',
+                        'after whats_changed',
+                        'before get_docs',
+                        'record_sync_info',
+                        ]
+        else:
+            expected = ['sync_exchange', 'record_sync_info']
+
+        called = []
+
+        def cb(state):
+            called.append(state)
+
+        self.set_trace_hook(cb, shallow=True)
+        self.st.sync_exchange([], 'replica', 0, None, self.receive_doc)
+        self.st.record_sync_info('replica', 0, 'T-sid')
+        self.assertEqual(expected, called)
+
 
 # The following tests need that the database have an index, so we fake one.
 
@@ -339,16 +656,56 @@ if getattr(couch.CouchDatabase, '_old_class', None) is None:
 sync_scenarios = []
 for name, scenario in COUCH_SCENARIOS:
     scenario = dict(scenario)
-    scenario['do_sync'] = test_sync.sync_via_synchronizer
+    scenario['do_sync'] = sync_via_synchronizer
     sync_scenarios.append((name, scenario))
     scenario = dict(scenario)
 
 
 class CouchDatabaseSyncTests(
-        TestWithScenarios, test_sync.DatabaseSyncTests, CouchDBTestCase):
+        TestWithScenarios,
+        DatabaseBaseTests,
+        CouchDBTestCase):
 
     scenarios = sync_scenarios
 
+    def create_database(self, replica_uid, sync_role=None):
+        if replica_uid == 'test' and sync_role is None:
+            # created up the chain by base class but unused
+            return None
+        db = self.create_database_for_role(replica_uid, sync_role)
+        if sync_role:
+            self._use_tracking[db] = (replica_uid, sync_role)
+        return db
+
+    def create_database_for_role(self, replica_uid, sync_role):
+        # hook point for reuse
+        return DatabaseBaseTests.create_database(self, replica_uid)
+
+    def copy_database(self, db, sync_role=None):
+        # DO NOT COPY OR REUSE THIS CODE OUTSIDE TESTS: COPYING U1DB DATABASES
+        # IS THE WRONG THING TO DO, THE ONLY REASON WE DO SO HERE IS TO TEST
+        # THAT WE CORRECTLY DETECT IT HAPPENING SO THAT WE CAN RAISE ERRORS
+        # RATHER THAN CORRUPT USER DATA. USE SYNC INSTEAD, OR WE WILL SEND
+        # NINJA TO YOUR HOUSE.
+        db_copy = self.copy_database_for_test(self, db)
+        name, orig_sync_role = self._use_tracking[db]
+        self._use_tracking[db_copy] = (name + '(copy)', sync_role
+                                       or orig_sync_role)
+        return db_copy
+
+    def sync(self, db_from, db_to, trace_hook=None,
+             trace_hook_shallow=None):
+        from_name, from_sync_role = self._use_tracking[db_from]
+        to_name, to_sync_role = self._use_tracking[db_to]
+        if from_sync_role not in ('source', 'both'):
+            raise Exception("%s marked for %s use but used as source" %
+                            (from_name, from_sync_role))
+        if to_sync_role not in ('target', 'both'):
+            raise Exception("%s marked for %s use but used as target" %
+                            (to_name, to_sync_role))
+        return self.do_sync(self, db_from, db_to, trace_hook,
+                            trace_hook_shallow)
+
     def setUp(self):
         self.db = None
         self.db1 = None
@@ -356,7 +713,8 @@ class CouchDatabaseSyncTests(
         self.db3 = None
         self.db1_copy = None
         self.db2_copy = None
-        test_sync.DatabaseSyncTests.setUp(self)
+        self._use_tracking = {}
+        DatabaseBaseTests.setUp(self)
 
     def tearDown(self):
         for db in [
@@ -375,7 +733,638 @@ class CouchDatabaseSyncTests(
             db.delete_database()
             # cleanup connections to avoid leaking of file descriptors
             db.close()
-        test_sync.DatabaseSyncTests.tearDown(self)
+        DatabaseBaseTests.tearDown(self)
+
+    def assertLastExchangeLog(self, db, expected):
+        log = getattr(db, '_last_exchange_log', None)
+        if log is None:
+            return
+        self.assertEqual(expected, log)
+
+    def test_sync_tracks_db_generation_of_other(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.assertEqual(0, self.sync(self.db1, self.db2))
+        self.assertEqual(
+            (0, ''), self.db1._get_replica_gen_and_trans_id('test2'))
+        self.assertEqual(
+            (0, ''), self.db2._get_replica_gen_and_trans_id('test1'))
+        self.assertLastExchangeLog(
+            self.db2,
+            {'receive': {'docs': [], 'last_known_gen': 0},
+             'return': {'docs': [], 'last_gen': 0}})
+
+    def test_sync_autoresolves(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        doc1 = self.db1.create_doc_from_json(simple_doc, doc_id='doc')
+        rev1 = doc1.rev
+        doc2 = self.db2.create_doc_from_json(simple_doc, doc_id='doc')
+        rev2 = doc2.rev
+        self.sync(self.db1, self.db2)
+        doc = self.db1.get_doc('doc')
+        self.assertFalse(doc.has_conflicts)
+        self.assertEqual(doc.rev, self.db2.get_doc('doc').rev)
+        v = vectorclock.VectorClockRev(doc.rev)
+        self.assertTrue(v.is_newer(vectorclock.VectorClockRev(rev1)))
+        self.assertTrue(v.is_newer(vectorclock.VectorClockRev(rev2)))
+
+    def test_sync_autoresolves_moar(self):
+        # here we test that when a database that has a conflicted document is
+        # the source of a sync, and the target database has a revision of the
+        # conflicted document that is newer than the source database's, and
+        # that target's database's document's content is the same as the
+        # source's document's conflict's, the source's document's conflict gets
+        # autoresolved, and the source's document's revision bumped.
+        #
+        # idea is as follows:
+        # A          B
+        # a1         -
+        #   `------->
+        # a1         a1
+        # v          v
+        # a2         a1b1
+        #   `------->
+        # a1b1+a2    a1b1
+        #            v
+        # a1b1+a2    a1b2 (a1b2 has same content as a2)
+        #   `------->
+        # a3b2       a1b2 (autoresolved)
+        #   `------->
+        # a3b2       a3b2
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db1.create_doc_from_json(simple_doc, doc_id='doc')
+        self.sync(self.db1, self.db2)
+        for db, content in [(self.db1, '{}'), (self.db2, '{"hi": 42}')]:
+            doc = db.get_doc('doc')
+            doc.set_json(content)
+            db.put_doc(doc)
+        self.sync(self.db1, self.db2)
+        # db1 and db2 now both have a doc of {hi:42}, but db1 has a conflict
+        doc = self.db1.get_doc('doc')
+        rev1 = doc.rev
+        self.assertTrue(doc.has_conflicts)
+        # set db2 to have a doc of {} (same as db1 before the conflict)
+        doc = self.db2.get_doc('doc')
+        doc.set_json('{}')
+        self.db2.put_doc(doc)
+        rev2 = doc.rev
+        # sync it across
+        self.sync(self.db1, self.db2)
+        # tadaa!
+        doc = self.db1.get_doc('doc')
+        self.assertFalse(doc.has_conflicts)
+        vec1 = vectorclock.VectorClockRev(rev1)
+        vec2 = vectorclock.VectorClockRev(rev2)
+        vec3 = vectorclock.VectorClockRev(doc.rev)
+        self.assertTrue(vec3.is_newer(vec1))
+        self.assertTrue(vec3.is_newer(vec2))
+        # because the conflict is on the source, sync it another time
+        self.sync(self.db1, self.db2)
+        # make sure db2 now has the exact same thing
+        self.assertEqual(self.db1.get_doc('doc'), self.db2.get_doc('doc'))
+
+    def test_sync_autoresolves_moar_backwards(self):
+        # here we test that when a database that has a conflicted document is
+        # the target of a sync, and the source database has a revision of the
+        # conflicted document that is newer than the target database's, and
+        # that source's database's document's content is the same as the
+        # target's document's conflict's, the target's document's conflict gets
+        # autoresolved, and the document's revision bumped.
+        #
+        # idea is as follows:
+        # A          B
+        # a1         -
+        #   `------->
+        # a1         a1
+        # v          v
+        # a2         a1b1
+        #   `------->
+        # a1b1+a2    a1b1
+        #            v
+        # a1b1+a2    a1b2 (a1b2 has same content as a2)
+        #   <-------'
+        # a3b2       a3b2 (autoresolved and propagated)
+        self.db1 = self.create_database('test1', 'both')
+        self.db2 = self.create_database('test2', 'both')
+        self.db1.create_doc_from_json(simple_doc, doc_id='doc')
+        self.sync(self.db1, self.db2)
+        for db, content in [(self.db1, '{}'), (self.db2, '{"hi": 42}')]:
+            doc = db.get_doc('doc')
+            doc.set_json(content)
+            db.put_doc(doc)
+        self.sync(self.db1, self.db2)
+        # db1 and db2 now both have a doc of {hi:42}, but db1 has a conflict
+        doc = self.db1.get_doc('doc')
+        rev1 = doc.rev
+        self.assertTrue(doc.has_conflicts)
+        revc = self.db1.get_doc_conflicts('doc')[-1].rev
+        # set db2 to have a doc of {} (same as db1 before the conflict)
+        doc = self.db2.get_doc('doc')
+        doc.set_json('{}')
+        self.db2.put_doc(doc)
+        rev2 = doc.rev
+        # sync it across
+        self.sync(self.db2, self.db1)
+        # tadaa!
+        doc = self.db1.get_doc('doc')
+        self.assertFalse(doc.has_conflicts)
+        vec1 = vectorclock.VectorClockRev(rev1)
+        vec2 = vectorclock.VectorClockRev(rev2)
+        vec3 = vectorclock.VectorClockRev(doc.rev)
+        vecc = vectorclock.VectorClockRev(revc)
+        self.assertTrue(vec3.is_newer(vec1))
+        self.assertTrue(vec3.is_newer(vec2))
+        self.assertTrue(vec3.is_newer(vecc))
+        # make sure db2 now has the exact same thing
+        self.assertEqual(self.db1.get_doc('doc'), self.db2.get_doc('doc'))
+
+    def test_sync_autoresolves_moar_backwards_three(self):
+        # same as autoresolves_moar_backwards, but with three databases (note
+        # all the syncs go in the same direction -- this is a more natural
+        # scenario):
+        #
+        # A          B          C
+        # a1         -          -
+        #   `------->
+        # a1         a1         -
+        #              `------->
+        # a1         a1         a1
+        # v          v
+        # a2         a1b1       a1
+        #  `------------------->
+        # a2         a1b1       a2
+        #              `------->
+        #            a2+a1b1    a2
+        #                       v
+        # a2         a2+a1b1    a2c1 (same as a1b1)
+        #  `------------------->
+        # a2c1       a2+a1b1    a2c1
+        #   `------->
+        # a2b2c1     a2b2c1     a2c1
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'both')
+        self.db3 = self.create_database('test3', 'target')
+        self.db1.create_doc_from_json(simple_doc, doc_id='doc')
+        self.sync(self.db1, self.db2)
+        self.sync(self.db2, self.db3)
+        for db, content in [(self.db2, '{"hi": 42}'),
+                            (self.db1, '{}'),
+                            ]:
+            doc = db.get_doc('doc')
+            doc.set_json(content)
+            db.put_doc(doc)
+        self.sync(self.db1, self.db3)
+        self.sync(self.db2, self.db3)
+        # db2 and db3 now both have a doc of {}, but db2 has a
+        # conflict
+        doc = self.db2.get_doc('doc')
+        self.assertTrue(doc.has_conflicts)
+        revc = self.db2.get_doc_conflicts('doc')[-1].rev
+        self.assertEqual('{}', doc.get_json())
+        self.assertEqual(self.db3.get_doc('doc').get_json(), doc.get_json())
+        self.assertEqual(self.db3.get_doc('doc').rev, doc.rev)
+        # set db3 to have a doc of {hi:42} (same as db2 before the conflict)
+        doc = self.db3.get_doc('doc')
+        doc.set_json('{"hi": 42}')
+        self.db3.put_doc(doc)
+        rev3 = doc.rev
+        # sync it across to db1
+        self.sync(self.db1, self.db3)
+        # db1 now has hi:42, with a rev that is newer than db2's doc
+        doc = self.db1.get_doc('doc')
+        rev1 = doc.rev
+        self.assertFalse(doc.has_conflicts)
+        self.assertEqual('{"hi": 42}', doc.get_json())
+        VCR = vectorclock.VectorClockRev
+        self.assertTrue(VCR(rev1).is_newer(VCR(self.db2.get_doc('doc').rev)))
+        # so sync it to db2
+        self.sync(self.db1, self.db2)
+        # tadaa!
+        doc = self.db2.get_doc('doc')
+        self.assertFalse(doc.has_conflicts)
+        # db2's revision of the document is strictly newer than db1's before
+        # the sync, and db3's before that sync way back when
+        self.assertTrue(VCR(doc.rev).is_newer(VCR(rev1)))
+        self.assertTrue(VCR(doc.rev).is_newer(VCR(rev3)))
+        self.assertTrue(VCR(doc.rev).is_newer(VCR(revc)))
+        # make sure both dbs now have the exact same thing
+        self.assertEqual(self.db1.get_doc('doc'), self.db2.get_doc('doc'))
+
+    def test_sync_puts_changes(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        doc = self.db1.create_doc_from_json(simple_doc)
+        self.assertEqual(1, self.sync(self.db1, self.db2))
+        self.assertGetDoc(self.db2, doc.doc_id, doc.rev, simple_doc, False)
+        self.assertEqual(1, self.db1._get_replica_gen_and_trans_id('test2')[0])
+        self.assertEqual(1, self.db2._get_replica_gen_and_trans_id('test1')[0])
+        self.assertLastExchangeLog(
+            self.db2,
+            {'receive': {'docs': [(doc.doc_id, doc.rev)],
+                         'source_uid': 'test1',
+                         'source_gen': 1, 'last_known_gen': 0},
+             'return': {'docs': [], 'last_gen': 1}})
+
+    def test_sync_pulls_changes(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        doc = self.db2.create_doc_from_json(simple_doc)
+        self.db1.create_index('test-idx', 'key')
+        self.assertEqual(0, self.sync(self.db1, self.db2))
+        self.assertGetDoc(self.db1, doc.doc_id, doc.rev, simple_doc, False)
+        self.assertEqual(1, self.db1._get_replica_gen_and_trans_id('test2')[0])
+        self.assertEqual(1, self.db2._get_replica_gen_and_trans_id('test1')[0])
+        self.assertLastExchangeLog(
+            self.db2,
+            {'receive': {'docs': [], 'last_known_gen': 0},
+             'return': {'docs': [(doc.doc_id, doc.rev)],
+                        'last_gen': 1}})
+        self.assertEqual([doc], self.db1.get_from_index('test-idx', 'value'))
+
+    def test_sync_pulling_doesnt_update_other_if_changed(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        doc = self.db2.create_doc_from_json(simple_doc)
+        # After the local side has sent its list of docs, before we start
+        # receiving the "targets" response, we update the local database with a
+        # new record.
+        # When we finish synchronizing, we can notice that something locally
+        # was updated, and we cannot tell c2 our new updated generation
+
+        def before_get_docs(state):
+            if state != 'before get_docs':
+                return
+            self.db1.create_doc_from_json(simple_doc)
+
+        self.assertEqual(0, self.sync(self.db1, self.db2,
+                                      trace_hook=before_get_docs))
+        self.assertLastExchangeLog(
+            self.db2,
+            {'receive': {'docs': [], 'last_known_gen': 0},
+             'return': {'docs': [(doc.doc_id, doc.rev)],
+                        'last_gen': 1}})
+        self.assertEqual(1, self.db1._get_replica_gen_and_trans_id('test2')[0])
+        # c2 should not have gotten a '_record_sync_info' call, because the
+        # local database had been updated more than just by the messages
+        # returned from c2.
+        self.assertEqual(
+            (0, ''), self.db2._get_replica_gen_and_trans_id('test1'))
+
+    def test_sync_doesnt_update_other_if_nothing_pulled(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db1.create_doc_from_json(simple_doc)
+
+        def no_record_sync_info(state):
+            if state != 'record_sync_info':
+                return
+            self.fail('SyncTarget.record_sync_info was called')
+        self.assertEqual(1, self.sync(self.db1, self.db2,
+                                      trace_hook_shallow=no_record_sync_info))
+        self.assertEqual(
+            1,
+            self.db2._get_replica_gen_and_trans_id(self.db1._replica_uid)[0])
+
+    def test_sync_ignores_convergence(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'both')
+        doc = self.db1.create_doc_from_json(simple_doc)
+        self.db3 = self.create_database('test3', 'target')
+        self.assertEqual(1, self.sync(self.db1, self.db3))
+        self.assertEqual(0, self.sync(self.db2, self.db3))
+        self.assertEqual(1, self.sync(self.db1, self.db2))
+        self.assertLastExchangeLog(
+            self.db2,
+            {'receive': {'docs': [(doc.doc_id, doc.rev)],
+                         'source_uid': 'test1',
+                         'source_gen': 1, 'last_known_gen': 0},
+             'return': {'docs': [], 'last_gen': 1}})
+
+    def test_sync_ignores_superseded(self):
+        self.db1 = self.create_database('test1', 'both')
+        self.db2 = self.create_database('test2', 'both')
+        doc = self.db1.create_doc_from_json(simple_doc)
+        doc_rev1 = doc.rev
+        self.db3 = self.create_database('test3', 'target')
+        self.sync(self.db1, self.db3)
+        self.sync(self.db2, self.db3)
+        new_content = '{"key": "altval"}'
+        doc.set_json(new_content)
+        self.db1.put_doc(doc)
+        doc_rev2 = doc.rev
+        self.sync(self.db2, self.db1)
+        self.assertLastExchangeLog(
+            self.db1,
+            {'receive': {'docs': [(doc.doc_id, doc_rev1)],
+                         'source_uid': 'test2',
+                         'source_gen': 1, 'last_known_gen': 0},
+             'return': {'docs': [(doc.doc_id, doc_rev2)],
+                        'last_gen': 2}})
+        self.assertGetDoc(self.db1, doc.doc_id, doc_rev2, new_content, False)
+
+    def test_sync_sees_remote_conflicted(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        doc1 = self.db1.create_doc_from_json(simple_doc)
+        doc_id = doc1.doc_id
+        doc1_rev = doc1.rev
+        self.db1.create_index('test-idx', 'key')
+        new_doc = '{"key": "altval"}'
+        doc2 = self.db2.create_doc_from_json(new_doc, doc_id=doc_id)
+        doc2_rev = doc2.rev
+        self.assertTransactionLog([doc1.doc_id], self.db1)
+        self.sync(self.db1, self.db2)
+        self.assertLastExchangeLog(
+            self.db2,
+            {'receive': {'docs': [(doc_id, doc1_rev)],
+                         'source_uid': 'test1',
+                         'source_gen': 1, 'last_known_gen': 0},
+             'return': {'docs': [(doc_id, doc2_rev)],
+                        'last_gen': 1}})
+        self.assertTransactionLog([doc_id, doc_id], self.db1)
+        self.assertGetDoc(self.db1, doc_id, doc2_rev, new_doc, True)
+        self.assertGetDoc(self.db2, doc_id, doc2_rev, new_doc, False)
+        from_idx = self.db1.get_from_index('test-idx', 'altval')[0]
+        self.assertEqual(doc2.doc_id, from_idx.doc_id)
+        self.assertEqual(doc2.rev, from_idx.rev)
+        self.assertTrue(from_idx.has_conflicts)
+        self.assertEqual([], self.db1.get_from_index('test-idx', 'value'))
+
+    def test_sync_sees_remote_delete_conflicted(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        doc1 = self.db1.create_doc_from_json(simple_doc)
+        doc_id = doc1.doc_id
+        self.db1.create_index('test-idx', 'key')
+        self.sync(self.db1, self.db2)
+        doc2 = self.make_document(doc1.doc_id, doc1.rev, doc1.get_json())
+        new_doc = '{"key": "altval"}'
+        doc1.set_json(new_doc)
+        self.db1.put_doc(doc1)
+        self.db2.delete_doc(doc2)
+        self.assertTransactionLog([doc_id, doc_id], self.db1)
+        self.sync(self.db1, self.db2)
+        self.assertLastExchangeLog(
+            self.db2,
+            {'receive': {'docs': [(doc_id, doc1.rev)],
+                         'source_uid': 'test1',
+                         'source_gen': 2, 'last_known_gen': 1},
+             'return': {'docs': [(doc_id, doc2.rev)],
+                        'last_gen': 2}})
+        self.assertTransactionLog([doc_id, doc_id, doc_id], self.db1)
+        self.assertGetDocIncludeDeleted(self.db1, doc_id, doc2.rev, None, True)
+        self.assertGetDocIncludeDeleted(
+            self.db2, doc_id, doc2.rev, None, False)
+        self.assertEqual([], self.db1.get_from_index('test-idx', 'value'))
+
+    def test_sync_local_race_conflicted(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        doc = self.db1.create_doc_from_json(simple_doc)
+        doc_id = doc.doc_id
+        doc1_rev = doc.rev
+        self.db1.create_index('test-idx', 'key')
+        self.sync(self.db1, self.db2)
+        content1 = '{"key": "localval"}'
+        content2 = '{"key": "altval"}'
+        doc.set_json(content2)
+        self.db2.put_doc(doc)
+        doc2_rev2 = doc.rev
+        triggered = []
+
+        def after_whatschanged(state):
+            if state != 'after whats_changed':
+                return
+            triggered.append(True)
+            doc = self.make_document(doc_id, doc1_rev, content1)
+            self.db1.put_doc(doc)
+
+        self.sync(self.db1, self.db2, trace_hook=after_whatschanged)
+        self.assertEqual([True], triggered)
+        self.assertGetDoc(self.db1, doc_id, doc2_rev2, content2, True)
+        from_idx = self.db1.get_from_index('test-idx', 'altval')[0]
+        self.assertEqual(doc.doc_id, from_idx.doc_id)
+        self.assertEqual(doc.rev, from_idx.rev)
+        self.assertTrue(from_idx.has_conflicts)
+        self.assertEqual([], self.db1.get_from_index('test-idx', 'value'))
+        self.assertEqual([], self.db1.get_from_index('test-idx', 'localval'))
+
+    def test_sync_propagates_deletes(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'both')
+        doc1 = self.db1.create_doc_from_json(simple_doc)
+        doc_id = doc1.doc_id
+        self.db1.create_index('test-idx', 'key')
+        self.sync(self.db1, self.db2)
+        self.db2.create_index('test-idx', 'key')
+        self.db3 = self.create_database('test3', 'target')
+        self.sync(self.db1, self.db3)
+        self.db1.delete_doc(doc1)
+        deleted_rev = doc1.rev
+        self.sync(self.db1, self.db2)
+        self.assertLastExchangeLog(
+            self.db2,
+            {'receive': {'docs': [(doc_id, deleted_rev)],
+                         'source_uid': 'test1',
+                         'source_gen': 2, 'last_known_gen': 1},
+             'return': {'docs': [], 'last_gen': 2}})
+        self.assertGetDocIncludeDeleted(
+            self.db1, doc_id, deleted_rev, None, False)
+        self.assertGetDocIncludeDeleted(
+            self.db2, doc_id, deleted_rev, None, False)
+        self.assertEqual([], self.db1.get_from_index('test-idx', 'value'))
+        self.assertEqual([], self.db2.get_from_index('test-idx', 'value'))
+        self.sync(self.db2, self.db3)
+        self.assertLastExchangeLog(
+            self.db3,
+            {'receive': {'docs': [(doc_id, deleted_rev)],
+                         'source_uid': 'test2',
+                         'source_gen': 2, 'last_known_gen': 0},
+             'return': {'docs': [], 'last_gen': 2}})
+        self.assertGetDocIncludeDeleted(
+            self.db3, doc_id, deleted_rev, None, False)
+
+    def test_sync_propagates_deletes_2(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db1.create_doc_from_json('{"a": "1"}', doc_id='the-doc')
+        self.sync(self.db1, self.db2)
+        doc1_2 = self.db2.get_doc('the-doc')
+        self.db2.delete_doc(doc1_2)
+        self.sync(self.db1, self.db2)
+        self.assertGetDocIncludeDeleted(
+            self.db1, 'the-doc', doc1_2.rev, None, False)
+
+    def test_sync_propagates_resolution(self):
+        self.db1 = self.create_database('test1', 'both')
+        self.db2 = self.create_database('test2', 'both')
+        doc1 = self.db1.create_doc_from_json('{"a": 1}', doc_id='the-doc')
+        db3 = self.create_database('test3', 'both')
+        self.sync(self.db2, self.db1)
+        self.assertEqual(
+            self.db1._get_generation_info(),
+            self.db2._get_replica_gen_and_trans_id(self.db1._replica_uid))
+        self.assertEqual(
+            self.db2._get_generation_info(),
+            self.db1._get_replica_gen_and_trans_id(self.db2._replica_uid))
+        self.sync(db3, self.db1)
+        # update on 2
+        doc2 = self.make_document('the-doc', doc1.rev, '{"a": 2}')
+        self.db2.put_doc(doc2)
+        self.sync(self.db2, db3)
+        self.assertEqual(db3.get_doc('the-doc').rev, doc2.rev)
+        # update on 1
+        doc1.set_json('{"a": 3}')
+        self.db1.put_doc(doc1)
+        # conflicts
+        self.sync(self.db2, self.db1)
+        self.sync(db3, self.db1)
+        self.assertTrue(self.db2.get_doc('the-doc').has_conflicts)
+        self.assertTrue(db3.get_doc('the-doc').has_conflicts)
+        # resolve
+        conflicts = self.db2.get_doc_conflicts('the-doc')
+        doc4 = self.make_document('the-doc', None, '{"a": 4}')
+        revs = [doc.rev for doc in conflicts]
+        self.db2.resolve_doc(doc4, revs)
+        doc2 = self.db2.get_doc('the-doc')
+        self.assertEqual(doc4.get_json(), doc2.get_json())
+        self.assertFalse(doc2.has_conflicts)
+        self.sync(self.db2, db3)
+        doc3 = db3.get_doc('the-doc')
+        self.assertEqual(doc4.get_json(), doc3.get_json())
+        self.assertFalse(doc3.has_conflicts)
+
+    def test_sync_supersedes_conflicts(self):
+        self.db1 = self.create_database('test1', 'both')
+        self.db2 = self.create_database('test2', 'target')
+        db3 = self.create_database('test3', 'both')
+        doc1 = self.db1.create_doc_from_json('{"a": 1}', doc_id='the-doc')
+        self.db2.create_doc_from_json('{"b": 1}', doc_id='the-doc')
+        db3.create_doc_from_json('{"c": 1}', doc_id='the-doc')
+        self.sync(db3, self.db1)
+        self.assertEqual(
+            self.db1._get_generation_info(),
+            db3._get_replica_gen_and_trans_id(self.db1._replica_uid))
+        self.assertEqual(
+            db3._get_generation_info(),
+            self.db1._get_replica_gen_and_trans_id(db3._replica_uid))
+        self.sync(db3, self.db2)
+        self.assertEqual(
+            self.db2._get_generation_info(),
+            db3._get_replica_gen_and_trans_id(self.db2._replica_uid))
+        self.assertEqual(
+            db3._get_generation_info(),
+            self.db2._get_replica_gen_and_trans_id(db3._replica_uid))
+        self.assertEqual(3, len(db3.get_doc_conflicts('the-doc')))
+        doc1.set_json('{"a": 2}')
+        self.db1.put_doc(doc1)
+        self.sync(db3, self.db1)
+        # original doc1 should have been removed from conflicts
+        self.assertEqual(3, len(db3.get_doc_conflicts('the-doc')))
+
+    def test_sync_stops_after_get_sync_info(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db1.create_doc_from_json(tests.simple_doc)
+        self.sync(self.db1, self.db2)
+
+        def put_hook(state):
+            self.fail("Tracehook triggered for %s" % (state,))
+
+        self.sync(self.db1, self.db2, trace_hook_shallow=put_hook)
+
+    def test_sync_detects_identical_replica_uid(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test1', 'target')
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id='doc1')
+        self.assertRaises(
+            u1db_errors.InvalidReplicaUID, self.sync, self.db1, self.db2)
+        # remove the reference to db2 to avoid double deleting on tearDown
+        self.db2.close()
+        self.db2 = None
+
+    def test_sync_detects_rollback_in_source(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id='doc1')
+        self.sync(self.db1, self.db2)
+        db1_copy = self.copy_database(self.db1)
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id='doc2')
+        self.sync(self.db1, self.db2)
+        self.assertRaises(
+            u1db_errors.InvalidGeneration, self.sync, db1_copy, self.db2)
+
+    def test_sync_detects_rollback_in_target(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id="divergent")
+        self.sync(self.db1, self.db2)
+        db2_copy = self.copy_database(self.db2)
+        self.db2.create_doc_from_json(tests.simple_doc, doc_id='doc2')
+        self.sync(self.db1, self.db2)
+        self.assertRaises(
+            u1db_errors.InvalidGeneration, self.sync, self.db1, db2_copy)
+
+    def test_sync_detects_diverged_source(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        db3 = self.copy_database(self.db1)
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id="divergent")
+        db3.create_doc_from_json(tests.simple_doc, doc_id="divergent")
+        self.sync(self.db1, self.db2)
+        self.assertRaises(
+            u1db_errors.InvalidTransactionId, self.sync, db3, self.db2)
+
+    def test_sync_detects_diverged_target(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        db3 = self.copy_database(self.db2)
+        db3.create_doc_from_json(tests.nested_doc, doc_id="divergent")
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id="divergent")
+        self.sync(self.db1, self.db2)
+        self.assertRaises(
+            u1db_errors.InvalidTransactionId, self.sync, self.db1, db3)
+
+    def test_sync_detects_rollback_and_divergence_in_source(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id='doc1')
+        self.sync(self.db1, self.db2)
+        db1_copy = self.copy_database(self.db1)
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id='doc2')
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id='doc3')
+        self.sync(self.db1, self.db2)
+        db1_copy.create_doc_from_json(tests.simple_doc, doc_id='doc2')
+        db1_copy.create_doc_from_json(tests.simple_doc, doc_id='doc3')
+        self.assertRaises(
+            u1db_errors.InvalidTransactionId, self.sync, db1_copy, self.db2)
+
+    def test_sync_detects_rollback_and_divergence_in_target(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id="divergent")
+        self.sync(self.db1, self.db2)
+        db2_copy = self.copy_database(self.db2)
+        self.db2.create_doc_from_json(tests.simple_doc, doc_id='doc2')
+        self.db2.create_doc_from_json(tests.simple_doc, doc_id='doc3')
+        self.sync(self.db1, self.db2)
+        db2_copy.create_doc_from_json(tests.simple_doc, doc_id='doc2')
+        db2_copy.create_doc_from_json(tests.simple_doc, doc_id='doc3')
+        self.assertRaises(
+            u1db_errors.InvalidTransactionId, self.sync, self.db1, db2_copy)
+
+    def test_optional_sync_preserve_json(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        cont1 = '{"a": 2}'
+        cont2 = '{"b": 3}'
+        self.db1.create_doc_from_json(cont1, doc_id="1")
+        self.db2.create_doc_from_json(cont2, doc_id="2")
+        self.sync(self.db1, self.db2)
+        self.assertEqual(cont1, self.db2.get_doc("1").get_json())
+        self.assertEqual(cont2, self.db1.get_doc("2").get_json())
 
 
 class CouchDatabaseExceptionsTests(CouchDBTestCase):
diff --git a/common/src/leap/soledad/common/tests/test_sqlcipher_sync.py b/common/src/leap/soledad/common/tests/test_sqlcipher_sync.py
index 5d368fdd..5a68f8b6 100644
--- a/common/src/leap/soledad/common/tests/test_sqlcipher_sync.py
+++ b/common/src/leap/soledad/common/tests/test_sqlcipher_sync.py
@@ -34,9 +34,7 @@ from leap.soledad.common import couch
 from leap.soledad.common.crypto import ENC_SCHEME_KEY
 from leap.soledad.client.http_target import SoledadHTTPSyncTarget
 from leap.soledad.client.crypto import decrypt_doc_dict
-from leap.soledad.client.sqlcipher import (
-    SQLCipherDatabase,
-)
+from leap.soledad.client.sqlcipher import SQLCipherDatabase
 
 from leap.soledad.common.tests import u1db_tests as tests
 from leap.soledad.common.tests.test_sqlcipher import SQLCIPHER_SCENARIOS
diff --git a/common/src/leap/soledad/common/tests/util.py b/common/src/leap/soledad/common/tests/util.py
index fe43986c..daa9c558 100644
--- a/common/src/leap/soledad/common/tests/util.py
+++ b/common/src/leap/soledad/common/tests/util.py
@@ -31,13 +31,14 @@ import subprocess
 import time
 import re
 import traceback
-from uuid import uuid4
 
+from uuid import uuid4
 from mock import Mock
 from urlparse import urljoin
 from StringIO import StringIO
 from pysqlcipher import dbapi2
 
+from u1db import sync
 from u1db.errors import DatabaseDoesNotExist
 from u1db.remote import http_database
 
@@ -55,20 +56,23 @@ from leap.soledad.client import Soledad
 from leap.soledad.client import http_target
 from leap.soledad.client import auth
 from leap.soledad.client.crypto import decrypt_doc_dict
+from leap.soledad.client.sqlcipher import SQLCipherDatabase
+from leap.soledad.client.sqlcipher import SQLCipherOptions
 
 from leap.soledad.server import SoledadApp
 from leap.soledad.server.auth import SoledadTokenAuthMiddleware
 
-from leap.soledad.client.sqlcipher import (
-    SQLCipherDatabase,
-    SQLCipherOptions,
-)
-
 
 PASSWORD = '123456'
 ADDRESS = 'leap@leap.se'
 
 
+def make_local_db_and_target(test):
+    db = test.create_database('test')
+    st = db.get_sync_target()
+    return db, st
+
+
 def make_sqlcipher_database_for_test(test, replica_uid):
     db = SQLCipherDatabase(
         SQLCipherOptions(':memory:', PASSWORD))
@@ -154,6 +158,15 @@ def copy_token_http_database_for_test(test, db):
     return http_db
 
 
+def sync_via_synchronizer(test, db_source, db_target, trace_hook=None,
+                          trace_hook_shallow=None):
+    target = db_target.get_sync_target()
+    trace_hook = trace_hook or trace_hook_shallow
+    if trace_hook:
+        target._set_trace_hook(trace_hook)
+    return sync.Synchronizer(db_source, target).sync()
+
+
 class MockedSharedDBTest(object):
 
     def get_default_shared_mock(self, put_doc_side_effect=None,