Пример #1
0
class TestCollectionRepo(TestCase):

    def setUp(self):
        assert_event_handlers_empty()
        # Setup the repo, and a persistence subscriber.
        stored_event_repo = PythonObjectsStoredEventRepository()
        event_store = EventStore(stored_event_repo=stored_event_repo)
        self.repo = CollectionRepo(event_store=event_store)
        self.ps = PersistenceSubscriber(event_store=event_store)

    def tearDown(self):
        self.ps.close()
        assert_event_handlers_empty()

    def test(self):
        # Check the collection is not in the repo.
        with self.assertRaises(RepositoryKeyError):
            _ = self.repo['none']

        # Register a new collection.
        collection_id = register_new_collection().id

        # Check the collection is in the repo.
        collection = self.repo[collection_id]
        self.assertIsInstance(collection, Collection)
        self.assertEqual(collection.id, collection_id)
        # Check the collection has zero items.
        self.assertEqual(len(collection.items), 0)

        # Add item.
        item1 = 'item1'
        collection.add_item(item1)

        # Check the collection is in the repo.
        collection = self.repo[collection_id]
        self.assertIsInstance(collection, Collection)
        self.assertEqual(collection.id, collection_id)
        # Check the collection has one item.
        self.assertEqual(len(collection.items), 1)

        # Remove item.
        collection.remove_item(item1)

        # Check the collection is in the repo.
        collection = self.repo[collection_id]
        self.assertIsInstance(collection, Collection)
        self.assertEqual(collection.id, collection_id)
        # Check the collection has zero items.
        self.assertEqual(len(collection.items), 0)

        # Discard the collection.
        collection.discard()

        # Check the collection is not in the repo.
        with self.assertRaises(RepositoryKeyError):
            _ = self.repo['none']
Пример #2
0
class TestCollectionRepo(TestCase):
    def setUp(self):
        assert_event_handlers_empty()
        # Setup the repo, and a persistence subscriber.
        stored_event_repo = PythonObjectsStoredEventRepository()
        event_store = EventStore(stored_event_repo=stored_event_repo)
        self.repo = CollectionRepo(event_store=event_store)
        self.ps = PersistenceSubscriber(event_store=event_store)

    def tearDown(self):
        self.ps.close()
        assert_event_handlers_empty()

    def test(self):
        # Check the collection is not in the repo.
        with self.assertRaises(RepositoryKeyError):
            _ = self.repo['none']

        # Register a new collection.
        collection_id = register_new_collection().id

        # Check the collection is in the repo.
        collection = self.repo[collection_id]
        self.assertIsInstance(collection, Collection)
        self.assertEqual(collection.id, collection_id)
        # Check the collection has zero items.
        self.assertEqual(len(collection.items), 0)

        # Add item.
        item1 = 'item1'
        collection.add_item(item1)

        # Check the collection is in the repo.
        collection = self.repo[collection_id]
        self.assertIsInstance(collection, Collection)
        self.assertEqual(collection.id, collection_id)
        # Check the collection has one item.
        self.assertEqual(len(collection.items), 1)

        # Remove item.
        collection.remove_item(item1)

        # Check the collection is in the repo.
        collection = self.repo[collection_id]
        self.assertIsInstance(collection, Collection)
        self.assertEqual(collection.id, collection_id)
        # Check the collection has zero items.
        self.assertEqual(len(collection.items), 0)

        # Discard the collection.
        collection.discard()

        # Check the collection is not in the repo.
        with self.assertRaises(RepositoryKeyError):
            _ = self.repo['none']
Пример #3
0
class TestPersistenceSubscriber(unittest.TestCase):
    def setUp(self):
        # Set up a persistence subscriber with a (mock) event store.
        self.event_store = mock.Mock(spec=AbstractEventStore)
        self.persistence_subscriber = PersistenceSubscriber(
            event_store=self.event_store)

    def tearDown(self):
        # Close the persistence subscriber.
        self.persistence_subscriber.close()

    def test_published_events_are_appended_to_event_store(self):
        # Check the event store's append method has NOT been called.
        self.assertEqual(0, self.event_store.append.call_count)

        # Publish a (mock) domain event.
        domain_event = mock.Mock(spec=DomainEvent)
        publish(domain_event)

        # Check the append method HAS been called once with the domain event.
        self.event_store.append.assert_called_once_with(domain_event)
class TestPersistenceSubscriber(unittest.TestCase):

    def setUp(self):
        # Set up a persistence subscriber with a (mock) event store.
        self.event_store = mock.Mock(spec=AbstractEventStore)
        self.persistence_subscriber = PersistenceSubscriber(event_store=self.event_store)

    def tearDown(self):
        # Close the persistence subscriber.
        self.persistence_subscriber.close()

    def test_published_events_are_appended_to_event_store(self):
        # Check the event store's append method has NOT been called.
        self.assertEqual(0, self.event_store.append.call_count)

        # Publish a (mock) domain event.
        domain_event = mock.Mock(spec=DomainEvent)
        publish(domain_event)

        # Check the append method HAS been called once with the domain event.
        self.event_store.append.assert_called_once_with(domain_event)
Пример #5
0
class TestExampleEntity(unittest.TestCase):
    def setUp(self):
        # Setup the persistence subscriber.
        self.event_store = EventStore(PythonObjectsStoredEventRepository())
        self.persistence_subscriber = PersistenceSubscriber(
            event_store=self.event_store)

    def tearDown(self):
        self.persistence_subscriber.close()
        assert_event_handlers_empty()

    def test_entity_lifecycle(self):
        # Check the factory creates an instance.
        example1 = register_new_example(a=1, b=2)
        self.assertIsInstance(example1, Example)

        # Check the properties of the Example class.
        self.assertEqual(1, example1.a)
        self.assertEqual(2, example1.b)

        # Check the properties of the EventSourcedEntity class.
        self.assertTrue(example1.id)
        self.assertEqual(1, example1.version)
        self.assertTrue(example1.created_on)

        # Check a second instance with the same values is not "equal" to the first.
        example2 = register_new_example(a=1, b=2)
        self.assertNotEqual(example1, example2)

        # Setup the repo.
        repo = ExampleRepo(self.event_store)

        # Check the example entities can be retrieved from the example repository.
        entity1 = repo[example1.id]
        self.assertIsInstance(entity1, Example)
        self.assertEqual(1, entity1.a)
        self.assertEqual(2, entity1.b)

        entity2 = repo[example2.id]
        self.assertIsInstance(entity2, Example)
        self.assertEqual(1, entity2.a)
        self.assertEqual(2, entity2.b)

        # Check the entity can be updated.
        entity1.a = 100
        self.assertEqual(100, repo[entity1.id].a)
        entity1.b = -200
        self.assertEqual(-200, repo[entity1.id].b)

        self.assertEqual(0, entity1.count_heartbeats())
        entity1.beat_heart()
        entity1.beat_heart()
        entity1.beat_heart()
        self.assertEqual(3, entity1.count_heartbeats())
        self.assertEqual(3, repo[entity1.id].count_heartbeats())

        # Check the entity can be discarded.
        entity1.discard()

        # Check the repo now raises a KeyError.
        self.assertRaises(RepositoryKeyError, repo.__getitem__, entity1.id)

        # Check the entity can't be discarded twice.
        self.assertRaises(AssertionError, entity1.discard)

        # Should fail to validate event with wrong entity ID.
        self.assertRaises(
            EntityIDConsistencyError, entity2._validate_originator,
            DomainEvent(entity_id=entity2.id + 'wrong', entity_version=0))
        # Should fail to validate event with wrong entity version.
        self.assertRaises(EntityVersionConsistencyError,
                          entity2._validate_originator,
                          DomainEvent(entity_id=entity2.id, entity_version=0))
        # Should validate event with correct entity ID and version.
        entity2._validate_originator(
            DomainEvent(entity_id=entity2.id, entity_version=entity2.version))

        # Check an entity can be reregistered with the same ID.
        replacement_event = Example.Created(entity_id=entity1.id, a=11, b=12)
        # replacement = Example.mutate(event=replacement_event)
        publish(event=replacement_event)

        # Check the replacement entity can be retrieved from the example repository.
        replacement = repo[entity1.id]
        assert isinstance(replacement, Example)
        self.assertEqual(replacement.a, 11)
        self.assertEqual(replacement.b, 12)

    def test_not_implemented_error(self):
        # Define an event class.
        class UnsupportedEvent(DomainEvent):
            pass

        # Check we get an error when attempting to mutate on the event.
        self.assertRaises(NotImplementedError, Example.mutate, Example,
                          UnsupportedEvent('1', '0'))

    def test_mutableproperty(self):
        # Check we get an error when called with something other than a function.
        self.assertRaises(ProgrammingError, mutableproperty, 'not a getter')
        self.assertRaises(ProgrammingError, mutableproperty, 123)
        self.assertRaises(ProgrammingError, mutableproperty, None)

        # Call the decorator with a function.
        getter = lambda: None
        p = mutableproperty(getter)

        # Check we got a property object.
        self.assertIsInstance(p, property)

        # Check the property object has both setter and getter functions.
        self.assertTrue(p.fset)
        self.assertTrue(p.fget)

        # Pretend we decorated an object.
        o = EventSourcedEntity(entity_id='1',
                               entity_version=0,
                               domain_event_id=1)
        o.__dict__['_<lambda>'] = 'value1'

        # Call the property's getter function.
        value = p.fget(o)
        self.assertEqual(value, 'value1')

        # Call the property's setter function.
        p.fset(o, 'value2')

        # Check the attribute has changed.
        value = p.fget(o)
        self.assertEqual(value, 'value2')

        # Check the property's getter function isn't the getter function we passed in.
        self.assertNotEqual(p.fget, getter)

        # Define a class that uses the decorator.
        class Aaa(EventSourcedEntity):
            "An event sourced entity."

            def __init__(self, a, *args, **kwargs):
                super(Aaa, self).__init__(*args, **kwargs)
                self._a = a

            @mutableproperty
            def a(self):
                "A mutable event sourced property."

        # Instantiate the class and check assigning to the property publishes an event and updates the object state.
        published_events = []
        subscription = (lambda x: True, lambda x: published_events.append(x))
        subscribe(*subscription)
        entity_id = '1'
        try:
            aaa = Aaa(entity_id=entity_id,
                      entity_version=None,
                      domain_event_id='0',
                      a=1)
            self.assertEqual(aaa.a, 1)
            aaa.a = 'value1'
            self.assertEqual(aaa.a, 'value1')
        finally:
            unsubscribe(*subscription)

        # Check an event was published.
        self.assertEqual(len(published_events), 1)

        # Check the published event was an AttributeChanged event, with the expected attribute values.
        published_event = published_events[0]
        self.assertIsInstance(published_event, Aaa.AttributeChanged)
        self.assertEqual(published_event.name, '_a')
        self.assertEqual(published_event.value, 'value1')
        self.assertTrue(published_event.domain_event_id)
        self.assertEqual(published_event.entity_id, entity_id)

    def test_static_mutator_method(self):
        self.assertRaises(NotImplementedError, EventSourcedEntity._mutator, 1,
                          2)

    def test_created_mutator_error(self):
        self.assertRaises(CreatedMutatorRequiresTypeNotInstance,
                          created_mutator, mock.Mock(spec=DomainEvent),
                          'not a class')
Пример #6
0
class TestExampleEntity(unittest.TestCase):

    def setUp(self):
        # Setup the persistence subscriber.
        self.event_store = EventStore(PythonObjectsStoredEventRepository())
        self.persistence_subscriber = PersistenceSubscriber(event_store=self.event_store)

    def tearDown(self):
        self.persistence_subscriber.close()
        assert_event_handlers_empty()

    def test_entity_lifecycle(self):
        # Check the factory creates an instance.
        example1 = register_new_example(a=1, b=2)
        self.assertIsInstance(example1, Example)

        # Check the properties of the Example class.
        self.assertEqual(1, example1.a)
        self.assertEqual(2, example1.b)

        # Check the properties of the EventSourcedEntity class.
        self.assertTrue(example1.id)
        self.assertEqual(1, example1.version)
        self.assertTrue(example1.created_on)

        # Check a second instance with the same values is not "equal" to the first.
        example2 = register_new_example(a=1, b=2)
        self.assertNotEqual(example1, example2)

        # Setup the repo.
        repo = ExampleRepo(self.event_store)

        # Check the example entities can be retrieved from the example repository.
        entity1 = repo[example1.id]
        self.assertIsInstance(entity1, Example)
        self.assertEqual(1, entity1.a)
        self.assertEqual(2, entity1.b)

        entity2 = repo[example2.id]
        self.assertIsInstance(entity2, Example)
        self.assertEqual(1, entity2.a)
        self.assertEqual(2, entity2.b)

        # Check the entity can be updated.
        entity1.a = 100
        self.assertEqual(100, repo[entity1.id].a)
        entity1.b = -200
        self.assertEqual(-200, repo[entity1.id].b)

        self.assertEqual(0, entity1.count_heartbeats())
        entity1.beat_heart()
        entity1.beat_heart()
        entity1.beat_heart()
        self.assertEqual(3, entity1.count_heartbeats())
        self.assertEqual(3, repo[entity1.id].count_heartbeats())

        # Check the entity can be discarded.
        entity1.discard()

        # Check the repo now raises a KeyError.
        self.assertRaises(RepositoryKeyError, repo.__getitem__, entity1.id)

        # Check the entity can't be discarded twice.
        self.assertRaises(AssertionError, entity1.discard)

        # Should fail to validate event with wrong entity ID.
        self.assertRaises(EntityIDConsistencyError,
                          entity2._validate_originator,
                          DomainEvent(entity_id=entity2.id+'wrong', entity_version=0)
                          )
        # Should fail to validate event with wrong entity version.
        self.assertRaises(EntityVersionConsistencyError,
                          entity2._validate_originator,
                          DomainEvent(entity_id=entity2.id, entity_version=0)
                          )
        # Should validate event with correct entity ID and version.
        entity2._validate_originator(
            DomainEvent(entity_id=entity2.id, entity_version=entity2.version)
        )

        # Check an entity can be reregistered with the same ID.
        replacement_event = Example.Created(entity_id=entity1.id, a=11, b=12)
        # replacement = Example.mutate(event=replacement_event)
        publish(event=replacement_event)

        # Check the replacement entity can be retrieved from the example repository.
        replacement = repo[entity1.id]
        assert isinstance(replacement, Example)
        self.assertEqual(replacement.a, 11)
        self.assertEqual(replacement.b, 12)

    def test_not_implemented_error(self):
        # Define an event class.
        class UnsupportedEvent(DomainEvent): pass

        # Check we get an error when attempting to mutate on the event.
        self.assertRaises(NotImplementedError, Example.mutate, Example, UnsupportedEvent('1', '0'))

    def test_mutableproperty(self):
        # Check we get an error when called with something other than a function.
        self.assertRaises(ProgrammingError, mutableproperty, 'not a getter')
        self.assertRaises(ProgrammingError, mutableproperty, 123)
        self.assertRaises(ProgrammingError, mutableproperty, None)

        # Call the decorator with a function.
        getter = lambda: None
        p = mutableproperty(getter)

        # Check we got a property object.
        self.assertIsInstance(p, property)

        # Check the property object has both setter and getter functions.
        self.assertTrue(p.fset)
        self.assertTrue(p.fget)

        # Pretend we decorated an object.
        o = EventSourcedEntity(entity_id='1', entity_version=0, domain_event_id=1)
        o.__dict__['_<lambda>'] = 'value1'

        # Call the property's getter function.
        value = p.fget(o)
        self.assertEqual(value, 'value1')

        # Call the property's setter function.
        p.fset(o, 'value2')

        # Check the attribute has changed.
        value = p.fget(o)
        self.assertEqual(value, 'value2')

        # Check the property's getter function isn't the getter function we passed in.
        self.assertNotEqual(p.fget, getter)

        # Define a class that uses the decorator.
        class Aaa(EventSourcedEntity):
            "An event sourced entity."

            def __init__(self, a, *args, **kwargs):
                super(Aaa, self).__init__(*args, **kwargs)
                self._a = a

            @mutableproperty
            def a(self):
                "A mutable event sourced property."

        # Instantiate the class and check assigning to the property publishes an event and updates the object state.
        published_events = []
        subscription = (lambda x: True, lambda x: published_events.append(x))
        subscribe(*subscription)
        entity_id = '1'
        try:
            aaa = Aaa(entity_id=entity_id, entity_version=None, domain_event_id='0', a=1)
            self.assertEqual(aaa.a, 1)
            aaa.a = 'value1'
            self.assertEqual(aaa.a, 'value1')
        finally:
            unsubscribe(*subscription)

        # Check an event was published.
        self.assertEqual(len(published_events), 1)

        # Check the published event was an AttributeChanged event, with the expected attribute values.
        published_event = published_events[0]
        self.assertIsInstance(published_event, Aaa.AttributeChanged)
        self.assertEqual(published_event.name, '_a')
        self.assertEqual(published_event.value, 'value1')
        self.assertTrue(published_event.domain_event_id)
        self.assertEqual(published_event.entity_id, entity_id)

    def test_static_mutator_method(self):
        self.assertRaises(NotImplementedError, EventSourcedEntity._mutator, 1, 2)

    def test_created_mutator_error(self):
        self.assertRaises(CreatedMutatorRequiresTypeNotInstance, created_mutator, mock.Mock(spec=DomainEvent), 'not a class')
Пример #7
0
class LogTestCase(AbstractTestCase):
    @property
    def stored_event_repo(self):
        """
        Returns a stored event repository.

        Concrete log test cases will provide this method.
        """
        raise NotImplementedError

    def setUp(self):
        super(LogTestCase, self).setUp()

        # Check we're starting clean, event handler-wise.
        assert_event_handlers_empty()

        # Setup the persistence subscriber.
        self.event_store = EventStore(self.stored_event_repo)
        self.persistence_subscriber = PersistenceSubscriber(event_store=self.event_store)

        self.log_repo = LogRepo(self.event_store)

    def tearDown(self):
        # Close the persistence subscriber.
        self.persistence_subscriber.close()

        super(LogTestCase, self).tearDown()

        # Check we finished clean, event handler-wise.
        assert_event_handlers_empty()

    def test_entity_lifecycle(self):
        log = self.log_repo.get_or_create(log_name='log1', bucket_size='year')
        self.assertIsInstance(log, Log)
        self.assertEqual(log.name, 'log1')
        self.assertEqual(log.bucket_size, 'year')

        # Test get_logger and get_log_reader().
        logger = get_logger(log)
        self.assertIsInstance(logger, Logger)
        message1 = 'This is message 1'
        message2 = 'This is message 2'
        message3 = 'This is message 3'
        message4 = 'This is message 4'
        message5 = 'This is message 5'
        message6 = 'This is message 6'
        event1 = logger.info(message1)
        event2 = logger.info(message2)
        event3 = logger.info(message3)
        halfway = uuid1().hex
        event4 = logger.info(message4)
        event5 = logger.info(message5)
        event6 = logger.info(message6)

        # Check we can get all the messages (query running in descending order).
        log_reader = get_log_reader(log, event_store=self.event_store)
        messages = list(log_reader.get_messages(is_ascending=False))
        self.assertEqual(len(messages), 6)
        self.assertEqual(messages[0], message6)
        self.assertEqual(messages[1], message5)
        self.assertEqual(messages[2], message4)
        self.assertEqual(messages[3], message3)
        self.assertEqual(messages[4], message2)
        self.assertEqual(messages[5], message1)

        # Check we can get all the messages (query running in ascending order).
        messages = list(log_reader.get_messages(is_ascending=True))
        self.assertEqual(len(messages), 6)
        self.assertEqual(messages[0], message1)
        self.assertEqual(messages[1], message2)
        self.assertEqual(messages[2], message3)
        self.assertEqual(messages[3], message4)
        self.assertEqual(messages[4], message5)
        self.assertEqual(messages[5], message6)

        # Check we can get messages after halfway (query running in descending order).
        messages = list(log_reader.get_messages(after=halfway, is_ascending=False))
        self.assertEqual(len(messages), 3)
        self.assertEqual(messages[0], message6)
        self.assertEqual(messages[1], message5)
        self.assertEqual(messages[2], message4)

        # Check we can get messages until halfway (query running in descending order).
        messages = list(log_reader.get_messages(until=halfway, is_ascending=False))
        self.assertEqual(len(messages), 3)
        self.assertEqual(messages[0], message3)
        self.assertEqual(messages[1], message2)
        self.assertEqual(messages[2], message1)

        # Check we can get messages until halfway (query running in ascending order).
        messages = list(log_reader.get_messages(until=halfway, is_ascending=True))
        self.assertEqual(len(messages), 3)
        self.assertEqual(messages[0], message1)
        self.assertEqual(messages[1], message2)
        self.assertEqual(messages[2], message3)

        # Check we can get messages after halfway (query running in ascending order).
        messages = list(log_reader.get_messages(after=halfway, is_ascending=True))
        self.assertEqual(len(messages), 3)
        self.assertEqual(messages[0], message4)
        self.assertEqual(messages[1], message5)
        self.assertEqual(messages[2], message6)

        # Check we can get last three messages (query running in descending order).
        messages = list(log_reader.get_messages(limit=3, is_ascending=False))
        self.assertEqual(len(messages), 3)
        self.assertEqual(messages[0], message6)
        self.assertEqual(messages[1], message5)
        self.assertEqual(messages[2], message4)

        # Check we can get first three messages (query running in ascending order).
        messages = list(log_reader.get_messages(limit=3, is_ascending=True))
        self.assertEqual(len(messages), 3)
        self.assertEqual(messages[0], message1)
        self.assertEqual(messages[1], message2)
        self.assertEqual(messages[2], message3)

        # Check we can get last line (query running in descending order).
        messages = list(log_reader.get_messages(limit=1, after=halfway, is_ascending=False))
        self.assertEqual(len(messages), 1)
        self.assertEqual(messages[0], message6)

        # Check we can get the first line after halfway (query running in ascending order).
        messages = list(log_reader.get_messages(limit=1, after=halfway, is_ascending=True))
        self.assertEqual(len(messages), 1)
        self.assertEqual(messages[0], message4)

        # Check we can get the first line before halfway (query running in descending order).
        messages = list(log_reader.get_messages(limit=1, until=halfway, is_ascending=False))
        self.assertEqual(len(messages), 1)
        self.assertEqual(messages[0], message3)

        # Check we can get the first line (query running in ascending order).
        messages = list(log_reader.get_messages(limit=1, until=halfway, is_ascending=True))
        self.assertEqual(len(messages), 1)
        self.assertEqual(messages[0], message1)

        # Check there isn't a line after the last line (query running in ascending order).
        messages = list(log_reader.get_messages(limit=1, after=event6.domain_event_id, is_ascending=True))
        self.assertEqual(len(messages), 0)

        # Check there is nothing somehow both after and until halfway.
        messages = list(log_reader.get_messages(after=halfway, until=halfway))
        self.assertEqual(len(messages), 0)

    def test_buckets(self):
        # Start new log.
        log = start_new_log(name='log1', bucket_size='second')

        # Write messages across the time interval
        start = datetime.datetime.now()
        logger = get_logger(log)
        number_of_messages = 300
        events = []
        for i in range(number_of_messages):
            message_logged = logger.info(str(i))
            events.append(message_logged)
            sleep(0.01)
        self.assertGreater(datetime.datetime.now() - start, datetime.timedelta(seconds=1))

        # Get the messages in descending order.
        reader = get_log_reader(log, self.event_store)
        messages = list(reader.get_messages(is_ascending=False, page_size=10))
        self.assertEqual(len(messages), number_of_messages)

        # Expect the order of the messages is the reverse of the created order.
        self.assertEqual(messages, list(reversed([str(i) for i in range(number_of_messages)])))

        # Get the messages in ascending order.
        messages = list(reader.get_messages(is_ascending=True, page_size=10))
        self.assertEqual(len(messages), number_of_messages)

        # Expect the order of the messages is the same as the created order.
        self.assertEqual(messages, [str(i) for i in range(number_of_messages)])

        # Get a limited number of messages in descending order.
        limit = 150
        messages = list(reader.get_messages(is_ascending=False, page_size=10, limit=limit))
        self.assertLess(limit, number_of_messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the reverse of the created order.
        self.assertEqual(messages, list(reversed([str(i) for i in range(number_of_messages)]))[:limit])

        # Get a limited number of messages in ascending order.
        limit = 150
        messages = list(reader.get_messages(is_ascending=True, page_size=10, limit=limit))
        self.assertLess(limit, number_of_messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the same as the created order.
        self.assertEqual(messages, [str(i) for i in range(limit)])

        # Get a limited number of messages in descending order from the midpoint down.
        limit = 110
        midpoint = events[150].domain_event_id
        messages = list(reader.get_messages(is_ascending=False, page_size=10, limit=limit, until=midpoint))
        self.assertLess(limit, number_of_messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the reverse of the created order.
        self.assertEqual(messages, list(reversed([str(i) for i in range(150 - limit, 150)])))

        # Get a limited number of messages in ascending order from the midpoint up.
        limit = 110
        midpoint = events[149].domain_event_id
        messages = list(reader.get_messages(is_ascending=True, page_size=10, limit=limit, after=midpoint))
        self.assertLess(limit, number_of_messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the same as the created order.
        self.assertEqual(messages, [str(i) for i in range(150, 150 + limit)])

        # Get a limited number of messages in descending order above the midpoint down.
        limit = 200
        midpoint = events[150].domain_event_id
        messages = list(reader.get_messages(is_ascending=False, page_size=10, limit=limit, after=midpoint))
        self.assertLess(limit, number_of_messages)
        self.assertEqual(len(messages), 150)

        # Expect the order of the messages is the reverse of the created order.
        self.assertEqual(messages, list(reversed([str(i) for i in range(150, 300)])))

        # Get a limited number of messages in ascending order below the midpoint up.
        limit = 200
        midpoint = events[149].domain_event_id
        messages = list(reader.get_messages(is_ascending=True, page_size=10, limit=limit, until=midpoint))
        self.assertLess(limit, number_of_messages)
        self.assertEqual(len(messages), 150)

        # Expect the order of the messages is the same as the created order.
        self.assertEqual(messages, [str(i) for i in range(150)])

        #
        # Use the last position to start part way through.
        limit = 20
        last_position = reader.position
        messages = reader.get_messages(is_ascending=True, page_size=10, limit=limit, after=last_position)
        messages = list(messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the same as the created order.
        self.assertEqual(messages, [str(i) for i in range(150, 150 + limit)])

        # Do it again.
        last_position = reader.position
        messages = reader.get_messages(is_ascending=True, page_size=10, limit=limit, after=last_position)
        messages = list(messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the same as the created order.
        self.assertEqual(messages, [str(i) for i in range(150 + limit, 150 + limit * 2)])

        # Go back.
        last_position = reader.position
        messages = reader.get_messages(is_ascending=False, page_size=10, limit=limit, until=last_position)
        messages = list(messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the reverse of the created order.
        self.assertEqual(messages, [str(i) for i in range(148 + limit * 2, 148 + limit, -1)])

        # Go back.
        last_position = reader.position
        messages = reader.get_messages(is_ascending=False, page_size=10, limit=limit, until=last_position)
        messages = list(messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the reverse of the created order.
        self.assertEqual(messages, [str(i) for i in range(128 + limit * 2, 128 + limit, -1)])

        # Go back.
        last_position = reader.position
        messages = reader.get_messages(is_ascending=False, page_size=10, limit=limit, until=last_position)
        messages = list(messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the reverse of the created order.
        self.assertEqual(messages, [str(i) for i in range(108 + limit * 2, 108 + limit, -1)])

        # Repeat.
        messages = reader.get_messages(is_ascending=False, page_size=10, limit=limit, until=last_position)
        messages = list(messages)
        self.assertEqual(len(messages), limit)

        # Expect the order of the messages is the reverse of the created order.
        self.assertEqual(messages, [str(i) for i in range(108 + limit * 2, 108 + limit, -1)])