[test] toxify tests

- move tests to root directory
- split tests in different subdirectories
- setup a small package with common test dependencies in /testing/test_soledad
- add tox.ini that will:
  - install the test_soledad package and other test dependencies
  - install soledad common, client, server from the repository
  - run tests contianed in /testing/tests directory using pytest

This commit also removes all oauth code from tests, as we have removed the
u1db dependency (by importing it into the repo and naming it l2db) and don't
neet oauth at all right now.

4 files changed, 1835 insertions, 0 deletions

diff --git a/testing/tests/couch/__init__.py b/testing/tests/couch/__init__.py
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/testing/tests/couch/__init__.py
diff --git a/testing/tests/couch/couchdb.ini.template b/testing/tests/couch/couchdb.ini.template
new file mode 100644
index 00000000..174d9d86
--- /dev/null
+++ b/testing/tests/couch/couchdb.ini.template
@@ -0,0 +1,22 @@
+; etc/couchdb/default.ini.tpl.  Generated from default.ini.tpl.in by configure.
+
+; Upgrading CouchDB will overwrite this file.
+
+[couchdb]
+database_dir = %(tempdir)s/lib
+view_index_dir = %(tempdir)s/lib
+max_document_size = 4294967296 ; 4 GB
+os_process_timeout = 120000 ; 120 seconds. for view and external servers.
+max_dbs_open = 100
+delayed_commits = true ; set this to false to ensure an fsync before 201 Created is returned
+uri_file = %(tempdir)s/lib/couch.uri
+file_compression = snappy
+
+[log]
+file = %(tempdir)s/log/couch.log
+level = info
+include_sasl = true
+
+[httpd]
+port = 0
+bind_address = 127.0.0.1
diff --git a/testing/tests/couch/test_couch.py b/testing/tests/couch/test_couch.py
new file mode 100644
index 00000000..94c6ca92
--- /dev/null
+++ b/testing/tests/couch/test_couch.py
@@ -0,0 +1,1442 @@
+# -*- coding: utf-8 -*-
+# test_couch.py
+# Copyright (C) 2013-2016 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+Test ObjectStore and Couch backend bits.
+"""
+import json
+
+from uuid import uuid4
+from urlparse import urljoin
+
+from couchdb.client import Server
+
+from testscenarios import TestWithScenarios
+from twisted.trial import unittest
+from mock import Mock
+
+from leap.soledad.common.l2db import errors as u1db_errors
+from leap.soledad.common.l2db import SyncTarget
+from leap.soledad.common.l2db import vectorclock
+
+from leap.soledad.common import couch
+from leap.soledad.common.document import ServerDocument
+from leap.soledad.common.couch import errors
+
+from test_soledad import u1db_tests as tests
+from test_soledad.util import CouchDBTestCase
+from test_soledad.util import make_local_db_and_target
+from test_soledad.util import sync_via_synchronizer
+
+from test_soledad.u1db_tests import test_backends
+from test_soledad.u1db_tests import DatabaseBaseTests
+
+
+# -----------------------------------------------------------------------------
+# The following tests come from `u1db.tests.test_common_backend`.
+# -----------------------------------------------------------------------------
+
+class TestCouchBackendImpl(CouchDBTestCase):
+
+    def test__allocate_doc_id(self):
+        db = couch.CouchDatabase.open_database(
+            urljoin(
+                'http://localhost:' + str(self.couch_port),
+                ('test-%s' % uuid4().hex)
+            ),
+            create=True,
+            ensure_ddocs=True)
+        doc_id1 = db._allocate_doc_id()
+        self.assertTrue(doc_id1.startswith('D-'))
+        self.assertEqual(34, len(doc_id1))
+        int(doc_id1[len('D-'):], 16)
+        self.assertNotEqual(doc_id1, db._allocate_doc_id())
+        self.delete_db(db._dbname)
+
+
+# -----------------------------------------------------------------------------
+# The following tests come from `u1db.tests.test_backends`.
+# -----------------------------------------------------------------------------
+
+def make_couch_database_for_test(test, replica_uid):
+    port = str(test.couch_port)
+    dbname = ('test-%s' % uuid4().hex)
+    db = couch.CouchDatabase.open_database(
+        urljoin('http://localhost:' + port, dbname),
+        create=True,
+        replica_uid=replica_uid or 'test',
+        ensure_ddocs=True)
+    test.addCleanup(test.delete_db, dbname)
+    return db
+
+
+def copy_couch_database_for_test(test, db):
+    port = str(test.couch_port)
+    couch_url = 'http://localhost:' + port
+    new_dbname = db._dbname + '_copy'
+    new_db = couch.CouchDatabase.open_database(
+        urljoin(couch_url, new_dbname),
+        create=True,
+        replica_uid=db._replica_uid or 'test')
+    # copy all docs
+    session = couch.Session()
+    old_couch_db = Server(couch_url, session=session)[db._dbname]
+    new_couch_db = Server(couch_url, session=session)[new_dbname]
+    for doc_id in old_couch_db:
+        doc = old_couch_db.get(doc_id)
+        # bypass u1db_config document
+        if doc_id == 'u1db_config':
+            pass
+        # copy design docs
+        elif doc_id.startswith('_design'):
+            del doc['_rev']
+            new_couch_db.save(doc)
+        # copy u1db docs
+        elif 'u1db_rev' in doc:
+            new_doc = {
+                '_id': doc['_id'],
+                'u1db_transactions': doc['u1db_transactions'],
+                'u1db_rev': doc['u1db_rev']
+            }
+            attachments = []
+            if ('u1db_conflicts' in doc):
+                new_doc['u1db_conflicts'] = doc['u1db_conflicts']
+                for c_rev in doc['u1db_conflicts']:
+                    attachments.append('u1db_conflict_%s' % c_rev)
+            new_couch_db.save(new_doc)
+            # save conflict data
+            attachments.append('u1db_content')
+            for att_name in attachments:
+                att = old_couch_db.get_attachment(doc_id, att_name)
+                if (att is not None):
+                    new_couch_db.put_attachment(new_doc, att,
+                                                filename=att_name)
+    # cleanup connections to prevent file descriptor leaking
+    return new_db
+
+
+def make_document_for_test(test, doc_id, rev, content, has_conflicts=False):
+    return ServerDocument(
+        doc_id, rev, content, has_conflicts=has_conflicts)
+
+
+COUCH_SCENARIOS = [
+    ('couch', {'make_database_for_test': make_couch_database_for_test,
+               'copy_database_for_test': copy_couch_database_for_test,
+               'make_document_for_test': make_document_for_test, }),
+]
+
+
+class CouchTests(
+        TestWithScenarios, test_backends.AllDatabaseTests, CouchDBTestCase):
+
+    scenarios = COUCH_SCENARIOS
+
+
+class SoledadBackendTests(
+        TestWithScenarios,
+        test_backends.LocalDatabaseTests,
+        CouchDBTestCase):
+
+    scenarios = COUCH_SCENARIOS
+
+
+class CouchValidateGenNTransIdTests(
+        TestWithScenarios,
+        test_backends.LocalDatabaseValidateGenNTransIdTests,
+        CouchDBTestCase):
+
+    scenarios = COUCH_SCENARIOS
+
+
+class CouchValidateSourceGenTests(
+        TestWithScenarios,
+        test_backends.LocalDatabaseValidateSourceGenTests,
+        CouchDBTestCase):
+
+    scenarios = COUCH_SCENARIOS
+
+
+class CouchWithConflictsTests(
+        TestWithScenarios,
+        test_backends.LocalDatabaseWithConflictsTests,
+        CouchDBTestCase):
+
+        scenarios = COUCH_SCENARIOS
+
+
+# Notice: the CouchDB backend does not have indexing capabilities, so we do
+# not test indexing now.
+
+# class CouchIndexTests(test_backends.DatabaseIndexTests, CouchDBTestCase):
+#
+#     scenarios = COUCH_SCENARIOS
+#
+#     def tearDown(self):
+#         self.db.delete_database()
+#         test_backends.DatabaseIndexTests.tearDown(self)
+
+
+# -----------------------------------------------------------------------------
+# The following tests come from `u1db.tests.test_sync`.
+# -----------------------------------------------------------------------------
+
+target_scenarios = [
+    ('local', {'create_db_and_target': make_local_db_and_target}), ]
+
+
+simple_doc = tests.simple_doc
+nested_doc = tests.nested_doc
+
+
+class SoledadBackendSyncTargetTests(
+        TestWithScenarios,
+        DatabaseBaseTests,
+        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)
+        # other stuff
+        self.db, self.st = self.create_db_and_target(self)
+        self.other_changes = []
+
+    def tearDown(self):
+        self.db.close()
+        CouchDBTestCase.tearDown(self)
+
+    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
+        # serialized representations).
+        doc = self.db.create_doc_from_json(simple_doc)
+        doc2 = self.db.create_doc_from_json(nested_doc)
+        self.assertTransactionLog([doc.doc_id, doc2.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, doc2.doc_id], self.db)
+        self.assertEqual(2, new_gen)
+        self.assertEqual(
+            [(doc.doc_id, doc.rev, json.loads(simple_doc), 1),
+             (doc2.doc_id, doc2.rev, json.loads(nested_doc), 2)],
+            [c[:-3] + (json.loads(c[-3]), c[-2]) for c in self.other_changes])
+        if self.whitebox:
+            self.assertEqual(
+                self.db._last_exchange_log['return'],
+                {'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):
+        st_trace_shallow = self.st._set_trace_hook_shallow
+        target_st_trace_shallow = SyncTarget._set_trace_hook_shallow
+        same_meth = st_trace_shallow == self.st._set_trace_hook
+        same_fun = st_trace_shallow.im_func == target_st_trace_shallow.im_func
+        if (same_meth or same_fun):
+            # 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)
+
+sync_scenarios = []
+for name, scenario in COUCH_SCENARIOS:
+    scenario = dict(scenario)
+    scenario['do_sync'] = sync_via_synchronizer
+    sync_scenarios.append((name, scenario))
+    scenario = dict(scenario)
+
+
+class SoledadBackendSyncTests(
+        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
+        self.db2 = None
+        self.db3 = None
+        self.db1_copy = None
+        self.db2_copy = None
+        self._use_tracking = {}
+        DatabaseBaseTests.setUp(self)
+
+    def tearDown(self):
+        for db in [
+            self.db, self.db1, self.db2,
+            self.db3, self.db1_copy, self.db2_copy
+        ]:
+            if db is not None:
+                self.delete_db(db._dbname)
+                db.close()
+        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.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.assertGetDoc(self.db2, doc.doc_id, doc.rev, simple_doc, False)
+
+    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
+        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)
+
+    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.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)
+
+    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.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)
+
+    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.sync(self.db1, self.db2)
+        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.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')
+        self.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(self.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, self.db3)
+        self.assertEqual(self.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(self.db3, self.db1)
+        self.assertTrue(self.db2.get_doc('the-doc').has_conflicts)
+        self.assertTrue(self.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, self.db3)
+        doc3 = self.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')
+        self.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')
+        self.db3.create_doc_from_json('{"c": 1}', doc_id='the-doc')
+        self.sync(self.db3, self.db1)
+        self.assertEqual(
+            self.db1._get_generation_info(),
+            self.db3._get_replica_gen_and_trans_id(self.db1._replica_uid))
+        self.assertEqual(
+            self.db3._get_generation_info(),
+            self.db1._get_replica_gen_and_trans_id(self.db3._replica_uid))
+        self.sync(self.db3, self.db2)
+        self.assertEqual(
+            self.db2._get_generation_info(),
+            self.db3._get_replica_gen_and_trans_id(self.db2._replica_uid))
+        self.assertEqual(
+            self.db3._get_generation_info(),
+            self.db2._get_replica_gen_and_trans_id(self.db3._replica_uid))
+        self.assertEqual(3, len(self.db3.get_doc_conflicts('the-doc')))
+        doc1.set_json('{"a": 2}')
+        self.db1.put_doc(doc1)
+        self.sync(self.db3, self.db1)
+        # original doc1 should have been removed from conflicts
+        self.assertEqual(3, len(self.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)
+
+    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)
+        self.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, self.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)
+        self.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, self.db2_copy)
+
+    def test_sync_detects_diverged_source(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db3 = self.copy_database(self.db1)
+        self.db1.create_doc_from_json(tests.simple_doc, doc_id="divergent")
+        self.db3.create_doc_from_json(tests.simple_doc, doc_id="divergent")
+        self.sync(self.db1, self.db2)
+        self.assertRaises(
+            u1db_errors.InvalidTransactionId, self.sync, self.db3, self.db2)
+
+    def test_sync_detects_diverged_target(self):
+        self.db1 = self.create_database('test1', 'source')
+        self.db2 = self.create_database('test2', 'target')
+        self.db3 = self.copy_database(self.db2)
+        self.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, self.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)
+        self.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)
+        self.db1_copy.create_doc_from_json(tests.simple_doc, doc_id='doc2')
+        self.db1_copy.create_doc_from_json(tests.simple_doc, doc_id='doc3')
+        self.assertRaises(
+            u1db_errors.InvalidTransactionId, self.sync,
+            self.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)
+        self.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)
+        self.db2_copy.create_doc_from_json(tests.simple_doc, doc_id='doc2')
+        self.db2_copy.create_doc_from_json(tests.simple_doc, doc_id='doc3')
+        self.assertRaises(
+            u1db_errors.InvalidTransactionId, self.sync,
+            self.db1, self.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 SoledadBackendExceptionsTests(CouchDBTestCase):
+
+    def setUp(self):
+        CouchDBTestCase.setUp(self)
+
+    def create_db(self, ensure=True, dbname=None):
+        if not dbname:
+            dbname = ('test-%s' % uuid4().hex)
+        if dbname not in self.couch_server:
+            self.couch_server.create(dbname)
+        self.db = couch.CouchDatabase(
+            ('http://127.0.0.1:%d' % self.couch_port),
+            dbname,
+            ensure_ddocs=ensure)
+
+    def tearDown(self):
+        self.db.delete_database()
+        self.db.close()
+        CouchDBTestCase.tearDown(self)
+
+    def test_missing_design_doc_raises(self):
+        """
+        Test that all methods that access design documents will raise if the
+        design docs are not present.
+        """
+        self.create_db(ensure=False)
+        # get_generation_info()
+        self.assertRaises(
+            errors.MissingDesignDocError,
+            self.db.get_generation_info)
+        # get_trans_id_for_gen()
+        self.assertRaises(
+            errors.MissingDesignDocError,
+            self.db.get_trans_id_for_gen, 1)
+        # get_transaction_log()
+        self.assertRaises(
+            errors.MissingDesignDocError,
+            self.db.get_transaction_log)
+        # whats_changed()
+        self.assertRaises(
+            errors.MissingDesignDocError,
+            self.db.whats_changed)
+
+    def test_missing_design_doc_functions_raises(self):
+        """
+        Test that all methods that access design documents list functions
+        will raise if the functions are not present.
+        """
+        self.create_db(ensure=True)
+        # erase views from _design/transactions
+        transactions = self.db._database['_design/transactions']
+        transactions['lists'] = {}
+        self.db._database.save(transactions)
+        # get_generation_info()
+        self.assertRaises(
+            errors.MissingDesignDocListFunctionError,
+            self.db.get_generation_info)
+        # get_trans_id_for_gen()
+        self.assertRaises(
+            errors.MissingDesignDocListFunctionError,
+            self.db.get_trans_id_for_gen, 1)
+        # whats_changed()
+        self.assertRaises(
+            errors.MissingDesignDocListFunctionError,
+            self.db.whats_changed)
+
+    def test_absent_design_doc_functions_raises(self):
+        """
+        Test that all methods that access design documents list functions
+        will raise if the functions are not present.
+        """
+        self.create_db(ensure=True)
+        # erase views from _design/transactions
+        transactions = self.db._database['_design/transactions']
+        del transactions['lists']
+        self.db._database.save(transactions)
+        # get_generation_info()
+        self.assertRaises(
+            errors.MissingDesignDocListFunctionError,
+            self.db.get_generation_info)
+        # _get_trans_id_for_gen()
+        self.assertRaises(
+            errors.MissingDesignDocListFunctionError,
+            self.db.get_trans_id_for_gen, 1)
+        # whats_changed()
+        self.assertRaises(
+            errors.MissingDesignDocListFunctionError,
+            self.db.whats_changed)
+
+    def test_missing_design_doc_named_views_raises(self):
+        """
+        Test that all methods that access design documents' named views  will
+        raise if the views are not present.
+        """
+        self.create_db(ensure=True)
+        # erase views from _design/docs
+        docs = self.db._database['_design/docs']
+        del docs['views']
+        self.db._database.save(docs)
+        # erase views from _design/syncs
+        syncs = self.db._database['_design/syncs']
+        del syncs['views']
+        self.db._database.save(syncs)
+        # erase views from _design/transactions
+        transactions = self.db._database['_design/transactions']
+        del transactions['views']
+        self.db._database.save(transactions)
+        # get_generation_info()
+        self.assertRaises(
+            errors.MissingDesignDocNamedViewError,
+            self.db.get_generation_info)
+        # _get_trans_id_for_gen()
+        self.assertRaises(
+            errors.MissingDesignDocNamedViewError,
+            self.db.get_trans_id_for_gen, 1)
+        # _get_transaction_log()
+        self.assertRaises(
+            errors.MissingDesignDocNamedViewError,
+            self.db.get_transaction_log)
+        # whats_changed()
+        self.assertRaises(
+            errors.MissingDesignDocNamedViewError,
+            self.db.whats_changed)
+
+    def test_deleted_design_doc_raises(self):
+        """
+        Test that all methods that access design documents will raise if the
+        design docs are not present.
+        """
+        self.create_db(ensure=True)
+        # delete _design/docs
+        del self.db._database['_design/docs']
+        # delete _design/syncs
+        del self.db._database['_design/syncs']
+        # delete _design/transactions
+        del self.db._database['_design/transactions']
+        # get_generation_info()
+        self.assertRaises(
+            errors.MissingDesignDocDeletedError,
+            self.db.get_generation_info)
+        # get_trans_id_for_gen()
+        self.assertRaises(
+            errors.MissingDesignDocDeletedError,
+            self.db.get_trans_id_for_gen, 1)
+        # get_transaction_log()
+        self.assertRaises(
+            errors.MissingDesignDocDeletedError,
+            self.db.get_transaction_log)
+        # whats_changed()
+        self.assertRaises(
+            errors.MissingDesignDocDeletedError,
+            self.db.whats_changed)
+
+    def test_ensure_ddoc_independently(self):
+        """
+        Test that a missing ddocs other than _design/docs will be ensured
+        even if _design/docs is there.
+        """
+        self.create_db(ensure=True)
+        del self.db._database['_design/transactions']
+        self.assertRaises(
+            errors.MissingDesignDocDeletedError,
+            self.db.get_transaction_log)
+        self.create_db(ensure=True, dbname=self.db._dbname)
+        self.db.get_transaction_log()
+
+    def test_ensure_security_doc(self):
+        """
+        Ensure_security creates a _security ddoc to ensure that only soledad
+        will have the lowest privileged access to an user db.
+        """
+        self.create_db(ensure=False)
+        self.assertFalse(self.db._database.resource.get_json('_security')[2])
+        self.db.ensure_security_ddoc()
+        security_ddoc = self.db._database.resource.get_json('_security')[2]
+        self.assertIn('admins', security_ddoc)
+        self.assertFalse(security_ddoc['admins']['names'])
+        self.assertIn('members', security_ddoc)
+        self.assertIn('soledad', security_ddoc['members']['names'])
+
+    def test_ensure_security_from_configuration(self):
+        """
+        Given a configuration, follow it to create the security document
+        """
+        self.create_db(ensure=False)
+        configuration = {'members': ['user1', 'user2'],
+                         'members_roles': ['role1', 'role2'],
+                         'admins': ['admin'],
+                         'admins_roles': ['administrators']
+                         }
+        self.db.ensure_security_ddoc(configuration)
+
+        security_ddoc = self.db._database.resource.get_json('_security')[2]
+        self.assertEquals(configuration['admins'],
+                          security_ddoc['admins']['names'])
+        self.assertEquals(configuration['admins_roles'],
+                          security_ddoc['admins']['roles'])
+        self.assertEquals(configuration['members'],
+                          security_ddoc['members']['names'])
+        self.assertEquals(configuration['members_roles'],
+                          security_ddoc['members']['roles'])
+
+
+class DatabaseNameValidationTest(unittest.TestCase):
+
+    def test_database_name_validation(self):
+        inject = couch.state.is_db_name_valid("user-deadbeef | cat /secret")
+        self.assertFalse(inject)
+        self.assertTrue(couch.state.is_db_name_valid("user-cafe1337"))
+
+
+class CommandBasedDBCreationTest(unittest.TestCase):
+
+    def test_ensure_db_using_custom_command(self):
+        state = couch.state.CouchServerState("url", create_cmd="echo")
+        mock_db = Mock()
+        mock_db.replica_uid = 'replica_uid'
+        state.open_database = Mock(return_value=mock_db)
+        db, replica_uid = state.ensure_database("user-1337")  # works
+        self.assertEquals(mock_db, db)
+        self.assertEquals(mock_db.replica_uid, replica_uid)
+
+    def test_raises_unauthorized_on_failure(self):
+        state = couch.state.CouchServerState("url", create_cmd="inexistent")
+        self.assertRaises(u1db_errors.Unauthorized,
+                          state.ensure_database, "user-1337")
+
+    def test_raises_unauthorized_by_default(self):
+        state = couch.state.CouchServerState("url")
+        self.assertRaises(u1db_errors.Unauthorized,
+                          state.ensure_database, "user-1337")
diff --git a/testing/tests/couch/test_couch_operations_atomicity.py b/testing/tests/couch/test_couch_operations_atomicity.py
new file mode 100644
index 00000000..aec9c6cf
--- /dev/null
+++ b/testing/tests/couch/test_couch_operations_atomicity.py
@@ -0,0 +1,371 @@
+# -*- coding: utf-8 -*-
+# test_couch_operations_atomicity.py
+# Copyright (C) 2013, 2014 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+Test atomicity of couch operations.
+"""
+import os
+import tempfile
+import threading
+
+from urlparse import urljoin
+from twisted.internet import defer
+from uuid import uuid4
+
+from leap.soledad.client import Soledad
+from leap.soledad.common.couch.state import CouchServerState
+from leap.soledad.common.couch import CouchDatabase
+
+from test_soledad.util import (
+    make_token_soledad_app,
+    make_soledad_document_for_test,
+    soledad_sync_target,
+)
+from test_soledad.util import CouchDBTestCase
+from test_soledad.u1db_tests import TestCaseWithServer
+
+
+REPEAT_TIMES = 20
+
+
+class CouchAtomicityTestCase(CouchDBTestCase, TestCaseWithServer):
+
+    @staticmethod
+    def make_app_after_state(state):
+        return make_token_soledad_app(state)
+
+    make_document_for_test = make_soledad_document_for_test
+
+    sync_target = soledad_sync_target
+
+    def _soledad_instance(self, user=None, passphrase=u'123',
+                          prefix='',
+                          secrets_path='secrets.json',
+                          local_db_path='soledad.u1db', server_url='',
+                          cert_file=None, auth_token=None):
+        """
+        Instantiate Soledad.
+        """
+        user = user or self.user
+
+        # this callback ensures we save a document which is sent to the shared
+        # db.
+        def _put_doc_side_effect(doc):
+            self._doc_put = doc
+
+        soledad = Soledad(
+            user,
+            passphrase,
+            secrets_path=os.path.join(self.tempdir, prefix, secrets_path),
+            local_db_path=os.path.join(
+                self.tempdir, prefix, local_db_path),
+            server_url=server_url,
+            cert_file=cert_file,
+            auth_token=auth_token,
+            shared_db=self.get_default_shared_mock(_put_doc_side_effect))
+        self.addCleanup(soledad.close)
+        return soledad
+
+    def make_app(self):
+        self.request_state = CouchServerState(self.couch_url)
+        return self.make_app_after_state(self.request_state)
+
+    def setUp(self):
+        TestCaseWithServer.setUp(self)
+        CouchDBTestCase.setUp(self)
+        self.user = ('user-%s' % uuid4().hex)
+        self.db = CouchDatabase.open_database(
+            urljoin(self.couch_url, 'user-' + self.user),
+            create=True,
+            replica_uid='replica',
+            ensure_ddocs=True)
+        self.tempdir = tempfile.mkdtemp(prefix="leap_tests-")
+        self.startTwistedServer()
+
+    def tearDown(self):
+        self.db.delete_database()
+        self.db.close()
+        CouchDBTestCase.tearDown(self)
+        TestCaseWithServer.tearDown(self)
+
+    #
+    # Sequential tests
+    #
+
+    def test_correct_transaction_log_after_sequential_puts(self):
+        """
+        Assert that the transaction_log increases accordingly with sequential
+        puts.
+        """
+        doc = self.db.create_doc({'ops': 0})
+        docs = [doc.doc_id]
+        for i in range(0, REPEAT_TIMES):
+            self.assertEqual(
+                i + 1, len(self.db._get_transaction_log()))
+            doc.content['ops'] += 1
+            self.db.put_doc(doc)
+            docs.append(doc.doc_id)
+
+        # assert length of transaction_log
+        transaction_log = self.db._get_transaction_log()
+        self.assertEqual(
+            REPEAT_TIMES + 1, len(transaction_log))
+
+        # assert that all entries in the log belong to the same doc
+        self.assertEqual(REPEAT_TIMES + 1, len(docs))
+        for doc_id in docs:
+            self.assertEqual(
+                REPEAT_TIMES + 1,
+                len(filter(lambda t: t[0] == doc_id, transaction_log)))
+
+    def test_correct_transaction_log_after_sequential_deletes(self):
+        """
+        Assert that the transaction_log increases accordingly with sequential
+        puts and deletes.
+        """
+        docs = []
+        for i in range(0, REPEAT_TIMES):
+            doc = self.db.create_doc({'ops': 0})
+            self.assertEqual(
+                2 * i + 1, len(self.db._get_transaction_log()))
+            docs.append(doc.doc_id)
+            self.db.delete_doc(doc)
+            self.assertEqual(
+                2 * i + 2, len(self.db._get_transaction_log()))
+
+        # assert length of transaction_log
+        transaction_log = self.db._get_transaction_log()
+        self.assertEqual(
+            2 * REPEAT_TIMES, len(transaction_log))
+
+        # assert that each doc appears twice in the transaction_log
+        self.assertEqual(REPEAT_TIMES, len(docs))
+        for doc_id in docs:
+            self.assertEqual(
+                2,
+                len(filter(lambda t: t[0] == doc_id, transaction_log)))
+
+    @defer.inlineCallbacks
+    def test_correct_sync_log_after_sequential_syncs(self):
+        """
+        Assert that the sync_log increases accordingly with sequential syncs.
+        """
+        sol = self._soledad_instance(
+            auth_token='auth-token',
+            server_url=self.getURL())
+        source_replica_uid = sol._dbpool.replica_uid
+
+        def _create_docs():
+            deferreds = []
+            for i in xrange(0, REPEAT_TIMES):
+                deferreds.append(sol.create_doc({}))
+            return defer.gatherResults(deferreds)
+
+        def _assert_transaction_and_sync_logs(results, sync_idx):
+            # assert sizes of transaction and sync logs
+            self.assertEqual(
+                sync_idx * REPEAT_TIMES,
+                len(self.db._get_transaction_log()))
+            gen, _ = self.db._get_replica_gen_and_trans_id(source_replica_uid)
+            self.assertEqual(sync_idx * REPEAT_TIMES, gen)
+
+        def _assert_sync(results, sync_idx):
+            gen, docs = results
+            self.assertEqual((sync_idx + 1) * REPEAT_TIMES, gen)
+            self.assertEqual((sync_idx + 1) * REPEAT_TIMES, len(docs))
+            # assert sizes of transaction and sync logs
+            self.assertEqual((sync_idx + 1) * REPEAT_TIMES,
+                             len(self.db._get_transaction_log()))
+            target_known_gen, target_known_trans_id = \
+                self.db._get_replica_gen_and_trans_id(source_replica_uid)
+            # assert it has the correct gen and trans_id
+            conn_key = sol._dbpool._u1dbconnections.keys().pop()
+            conn = sol._dbpool._u1dbconnections[conn_key]
+            sol_gen, sol_trans_id = conn._get_generation_info()
+            self.assertEqual(sol_gen, target_known_gen)
+            self.assertEqual(sol_trans_id, target_known_trans_id)
+
+        # sync first time and assert success
+        results = yield _create_docs()
+        _assert_transaction_and_sync_logs(results, 0)
+        yield sol.sync()
+        results = yield sol.get_all_docs()
+        _assert_sync(results, 0)
+
+        # create more docs, sync second time and assert success
+        results = yield _create_docs()
+        _assert_transaction_and_sync_logs(results, 1)
+        yield sol.sync()
+        results = yield sol.get_all_docs()
+        _assert_sync(results, 1)
+
+    #
+    # Concurrency tests
+    #
+
+    class _WorkerThread(threading.Thread):
+
+        def __init__(self, params, run_method):
+            threading.Thread.__init__(self)
+            self._params = params
+            self._run_method = run_method
+
+        def run(self):
+            self._run_method(self)
+
+    def test_correct_transaction_log_after_concurrent_puts(self):
+        """
+        Assert that the transaction_log increases accordingly with concurrent
+        puts.
+        """
+        pool = threading.BoundedSemaphore(value=1)
+        threads = []
+        docs = []
+
+        def _run_method(self):
+            doc = self._params['db'].create_doc({})
+            pool.acquire()
+            self._params['docs'].append(doc.doc_id)
+            pool.release()
+
+        for i in range(0, REPEAT_TIMES):
+            thread = self._WorkerThread(
+                {'docs': docs, 'db': self.db},
+                _run_method)
+            thread.start()
+            threads.append(thread)
+
+        for thread in threads:
+            thread.join()
+
+        # assert length of transaction_log
+        transaction_log = self.db._get_transaction_log()
+        self.assertEqual(
+            REPEAT_TIMES, len(transaction_log))
+
+        # assert all documents are in the log
+        self.assertEqual(REPEAT_TIMES, len(docs))
+        for doc_id in docs:
+            self.assertEqual(
+                1,
+                len(filter(lambda t: t[0] == doc_id, transaction_log)))
+
+    def test_correct_transaction_log_after_concurrent_deletes(self):
+        """
+        Assert that the transaction_log increases accordingly with concurrent
+        puts and deletes.
+        """
+        threads = []
+        docs = []
+        pool = threading.BoundedSemaphore(value=1)
+
+        # create/delete method that will be run concurrently
+        def _run_method(self):
+            doc = self._params['db'].create_doc({})
+            pool.acquire()
+            docs.append(doc.doc_id)
+            pool.release()
+            self._params['db'].delete_doc(doc)
+
+        # launch concurrent threads
+        for i in range(0, REPEAT_TIMES):
+            thread = self._WorkerThread({'db': self.db}, _run_method)
+            thread.start()
+            threads.append(thread)
+
+        # wait for threads to finish
+        for thread in threads:
+            thread.join()
+
+        # assert transaction log
+        transaction_log = self.db._get_transaction_log()
+        self.assertEqual(
+            2 * REPEAT_TIMES, len(transaction_log))
+        # assert that each doc appears twice in the transaction_log
+        self.assertEqual(REPEAT_TIMES, len(docs))
+        for doc_id in docs:
+            self.assertEqual(
+                2,
+                len(filter(lambda t: t[0] == doc_id, transaction_log)))
+
+    def test_correct_sync_log_after_concurrent_puts_and_sync(self):
+        """
+        Assert that the sync_log is correct after concurrent syncs.
+        """
+        docs = []
+
+        sol = self._soledad_instance(
+            auth_token='auth-token',
+            server_url=self.getURL())
+
+        def _save_doc_ids(results):
+            for doc in results:
+                docs.append(doc.doc_id)
+
+        # create documents in parallel
+        deferreds = []
+        for i in range(0, REPEAT_TIMES):
+            d = sol.create_doc({})
+            deferreds.append(d)
+
+        # wait for documents creation and sync
+        d = defer.gatherResults(deferreds)
+        d.addCallback(_save_doc_ids)
+        d.addCallback(lambda _: sol.sync())
+
+        def _assert_logs(results):
+            transaction_log = self.db._get_transaction_log()
+            self.assertEqual(REPEAT_TIMES, len(transaction_log))
+            # assert all documents are in the remote log
+            self.assertEqual(REPEAT_TIMES, len(docs))
+            for doc_id in docs:
+                self.assertEqual(
+                    1,
+                    len(filter(lambda t: t[0] == doc_id, transaction_log)))
+
+        d.addCallback(_assert_logs)
+        d.addCallback(lambda _: sol.close())
+
+        return d
+
+    @defer.inlineCallbacks
+    def test_concurrent_syncs_do_not_fail(self):
+        """
+        Assert that concurrent attempts to sync end up being executed
+        sequentially and do not fail.
+        """
+        docs = []
+
+        sol = self._soledad_instance(
+            auth_token='auth-token',
+            server_url=self.getURL())
+
+        deferreds = []
+        for i in xrange(0, REPEAT_TIMES):
+            d = sol.create_doc({})
+            d.addCallback(lambda doc: docs.append(doc.doc_id))
+            d.addCallback(lambda _: sol.sync())
+            deferreds.append(d)
+        yield defer.gatherResults(deferreds, consumeErrors=True)
+
+        transaction_log = self.db._get_transaction_log()
+        self.assertEqual(REPEAT_TIMES, len(transaction_log))
+        # assert all documents are in the remote log
+        self.assertEqual(REPEAT_TIMES, len(docs))
+        for doc_id in docs:
+            self.assertEqual(
+                1,
+                len(filter(lambda t: t[0] == doc_id, transaction_log)))