test_date.py

from pytest import fixture, mark
from sqlalchemy import (
    create_engine,
    Column,
    String,
    Integer,
    ForeignKey
)
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy.sql import select
from sqlalchemy.sql.expression import union, literal, alias
from itertools import chain
from subprocess import call
from datetime import date

Base = declarative_base()


@fixture()
def mysql(request):
    call(('docker run -itd --name testdb -p 3306:3306 '
          '-e MYSQL_ROOT_PASSWORD=root percona'), shell=True)
    def fin():
        call('docker rm -f testdb')
    request.addfinilizer(fin)
    return create_engine('mysql://root:root@127.0.0.1:3306')



@fixture()
def sqlite():
    return create_engine('sqlite:///:memory:')


@fixture(params=('sqlite', 'mysql'))
def session(request):
    engine = request.getfuncargvalue(request.param)
    Base.metadata.create_all(engine)
    return sessionmaker(bind=engine)()


def test_date(session):
    dates = (
        date(2016, 1, 1),
        date(2016, 1, 2),
    )
    selects = tuple(select((literal(d),)) for d in dates)
    data = alias(union(*selects, use_labels=True), 'dates') 
    stmt = select((data,))
    result = session.execute(stmt).fetchall()
    assert tuple(chain.from_iterable(result)) == dates