sqlalchemy test isolation

gistfile1.py

@pytest.fixture(scope='session')
def db(app, request):
    _db.create_all()

    def teardown():
        _db.session.remove()
        _db.drop_all()

    request.addfinalizer(teardown)
    return _db


@pytest.fixture(scope='function', autouse=True)
def transact(request, db, monkeypatch):
    request.addfinalizer(db.session.remove)
    monkeypatch.setattr(db.session, 'commit', db.session.flush)
    monkeypatch.setattr(db.session, 'remove', lambda: None)