How to use the vdirsyncer.storage.memory.MemoryStorage function in vdirsyncer

def test_no_uids():
    a = MemoryStorage()
    b = MemoryStorage()
    a.upload(Item('ASDF'))
    b.upload(Item('FOOBAR'))
    status = {}
    sync(a, b, status)
    assert items(a) == items(b) == {'ASDF', 'FOOBAR'}

def test_deletion():
    a = MemoryStorage(fileext='.a')
    b = MemoryStorage(fileext='.b')
    status = {}

    item = Item('UID:1')
    a.upload(item)
    item2 = Item('UID:2')
    a.upload(item2)
    sync(a, b, status)
    b.delete('1.b', b.get('1.b')[1])
    sync(a, b, status)
    assert items(a) == items(b) == {item2.raw}

    a.upload(item)
    sync(a, b, status)
    assert items(a) == items(b) == {item.raw, item2.raw}
    a.delete('1.a', a.get('1.a')[1])
    sync(a, b, status)

def test_updated_and_deleted():
    a = MemoryStorage()
    b = MemoryStorage()
    href_a, etag_a = a.upload(Item('UID:1'))
    status = {}
    sync(a, b, status, force_delete=True)

    (href_b, etag_b), = b.list()
    b.delete(href_b, etag_b)
    updated = Item('UID:1\nupdated')
    a.update(href_a, updated, etag_a)
    sync(a, b, status, force_delete=True)

    assert items(a) == items(b) == {updated.raw}

def test_conflict_resolution_invalid_mode():
    a = MemoryStorage()
    b = MemoryStorage()
    item_a = Item('UID:1\nitem a')
    item_b = Item('UID:1\nitem b')
    a.upload(item_a)
    b.upload(item_b)
    with pytest.raises(ValueError):
        sync(a, b, {}, conflict_resolution='yolo')

def test_insert_hash():
    a = MemoryStorage()
    b = MemoryStorage()
    status = {}

    item = Item('UID:1')
    href, etag = a.upload(item)
    sync(a, b, status)

    for d in status['1']:
        del d['hash']

    a.update(href, Item('UID:1\nHAHA:YES'), etag)
    sync(a, b, status)
    assert 'hash' in status['1'][0] and 'hash' in status['1'][1]

def test_duplicate_hrefs():
    a = MemoryStorage()
    b = MemoryStorage()
    a.list = lambda: [('a', 'a')] * 3
    a.items['a'] = ('a', Item('UID:a'))

    status = {}
    sync(a, b, status)
    with pytest.raises(AssertionError):
        sync(a, b, status)

def test_repair_uids(uid):
    s = MemoryStorage()
    s.items = {
        'one': (
            'asdf',
            Item('BEGIN:VCARD\nFN:Hans\nUID:{}\nEND:VCARD'.format(uid))
        ),
        'two': (
            'asdf',
            Item('BEGIN:VCARD\nFN:Peppi\nUID:{}\nEND:VCARD'.format(uid))
        )
    }

    uid1, uid2 = [s.get(href)[0].uid for href, etag in s.list()]
    assert uid1 == uid2

    repair_storage(s, repair_unsafe_uid=False)

def test_moved_href():
    '''
    Concrete application: ppl_ stores contact aliases in filenames, which means
    item's hrefs get changed. Vdirsyncer doesn't synchronize this data, but
    also shouldn't do things like deleting and re-uploading to the server.

    .. _ppl: http://ppladdressbook.org/
    '''
    a = MemoryStorage()
    b = MemoryStorage()
    status = {}
    href, etag = a.upload(Item('UID:haha'))
    sync(a, b, status)

    b.items['lol'] = b.items.pop('haha')

    # The sync algorithm should prefetch `lol`, see that it's the same ident
    # and not do anything else.
    a.get_multi = blow_up  # Absolutely no prefetch on A
    # No actual sync actions
    a.delete = a.update = a.upload = b.delete = b.update = b.upload = blow_up

    sync(a, b, status)
    assert len(status) == 1
    assert items(a) == items(b) == {'UID:haha'}
    assert status['haha'][1]['href'] == 'lol'

def test_conflict_resolution_invalid_mode():
    a = MemoryStorage()
    b = MemoryStorage()
    item_a = Item('UID:1\nitem a')
    item_b = Item('UID:1\nitem b')
    a.upload(item_a)
    b.upload(item_b)
    with pytest.raises(ValueError):
        sync(a, b, {}, conflict_resolution='yolo')

def test_conflict_x_wins(wins):
    a = MemoryStorage()
    b = MemoryStorage()
    status = {}
    a.set_meta('foo', 'bar')
    b.set_meta('foo', 'baz')

    metasync(a, b, status, keys=['foo'],
             conflict_resolution='a wins' if wins == 'a' else 'b wins')

    assert a.get_meta('foo') == b.get_meta('foo') == status['foo'] == (
        'bar' if wins == 'a' else 'baz'
    )