Flask unit test creates extra entry in database

I have a university task to create a flask app for car rental. When I manually(with Postman) create new order in the database, everything works good, but when I create the entry using test, it creates 1 extra(invalid) entry with almost the same info(except carId and userId). It happens when I try to run both tests(test_place_order and test_unauthorized).

test_flask.py:

class TestPlaceOrder(BaseTestCase):
    def setUp(self):
        super().setUp()
        self.car_1 = dbu.create_entry(car_table, **self.car_1_data)
        self.order_1 = dbu.create_entry(order_table, **self.order_1_data)
        self.user = dbu.create_entry(user_table, **self.user_1_credentials)

    def test_place_order(self):
        resp = self.client.post(
            url_for("api.place_order", carId=self.car_1.carId),
            json={"shipDate": self.order_1_data["shipDate"], "returnDate": self.order_1_data["returnDate"]},
            headers=self.get_auth_headers(self.user_1_credentials),
        )

        self.assertEqual(resp.status_code, 200)
        self.assertEqual(resp.json, {
            'id': ANY
        })
        self.assertTrue(
            Session().query(order_table).filter_by(shipDate=self.order_1.shipDate,
                                                   returnDate=self.order_1.returnDate).one()
        )

Post method:

@api_blueprint.route("/cars/car/<int:carId>/order", methods=["POST"])
@jwt_required
def place_order(carId):
    with session_scope():
        current_user = get_jwt_identity()
        user = dbu.get_entry_by_username(user_table, current_user)
        if current_user:
            order_data = OrderQuery().load(request.json)
            order = dbu.create_entry(order_table,
                                     userId=user.id,
                                     carId=carId,
                                     shipDate=order_data["shipDate"],
                                     returnDate=order_data["returnDate"],
                                     status="placed",
                                     complete=False)
            return jsonify({"id": OrderDetails().dump(order)["id"]})
        else:
            return jsonify(code=401, type="UNAUTHORIZED_ACCESS"), 401