Set and Get keys to and from a database

setgetdb.py

from tornado import web
from tornado.ioloop import IOLoop


class SetGetDB(web.RequestHandler):
    def initialize(self, db):
        self.db = db

    def post(self):
        args = self.request.query_arguments
        elements = {k: v[0].decode() for k, v in args.items()}
        self.db.update(elements)
        self.set_status(201)
        self.finish()

    def get(self):
        key = self.get_argument("key")
        if key in self.db:
            self.set_status(200)
            self.write(self.db[key])
        else:
            self.set_status(404)
        self.finish()


def build_app():
    db = {}

    application = web.Application([
        ("/set", SetGetDB, dict(db=db)),
        ("/get", SetGetDB, dict(db=db)),
    ])

    return application


def run(port=4000):
    application = build_app()

    application.listen(port)
    IOLoop.current().start()


if __name__ == "__main__":
    run()

test_setgetdb.py

import pytest
from tornado.httputil import url_concat
from tornado.httpclient import HTTPError

from setgetdb import build_app


@pytest.fixture
def app():
    return build_app()


@pytest.mark.gen_test
def test_set_valid_value(http_client, base_url):
    post_url = url_concat(base_url+"/set", dict(k="v"))

    response = yield http_client.fetch(post_url, method="POST", body="")
    assert response.code == 201

    get_url = url_concat(base_url+"/get", dict(key="k"))
    response_get = yield http_client.fetch(get_url)
    assert response_get.code == 200
    assert response_get.body.decode() == "v"


@pytest.mark.gen_test
def test_get_inexistent_key_should_return_not_found(http_client, base_url):
    get_url = url_concat(base_url+"/get", dict(key="_inexistent_key_"))
    with pytest.raises(HTTPError) as error:
        yield http_client.fetch(get_url)
    assert error.match(r"^HTTP 404.*")


@pytest.mark.gen_test
def test_rewrite_value_updates_to_new_value(http_client, base_url):
    post_url_1 = url_concat(base_url+"/set", dict(k="1"))
    yield http_client.fetch(post_url_1, method="POST", body="")

    get_url_1 = url_concat(base_url+"/get", dict(key="k"))
    response_get_1 = yield http_client.fetch(get_url_1)
    assert response_get_1.body.decode() == "1"

    post_url_2 = url_concat(base_url+"/set", dict(k="2"))
    yield http_client.fetch(post_url_2, method="POST", body="")

    get_url_2 = url_concat(base_url+"/get", dict(key="k"))
    response_get_2 = yield http_client.fetch(get_url_2)
    assert response_get_2.body.decode() == "2"