The existing posts didn't provide a useful answer to me.
I'm trying to run asynchronous database tests using Pytest (db is Postgres with asyncpg), and I'd like to initialize my database using my Alembic migrations so that I can verify that they work properly in the meantime.
My first attempt was this:
#pytest.fixture(scope="session")
async def tables():
"""Initialize a database before the tests, and then tear it down again"""
alembic_config: config.Config = config.Config('alembic.ini')
command.upgrade(alembic_config, "head")
yield
command.downgrade(alembic_config, "base")
which didn't actually do anything at all (migrations were never applied to the database, tables not created).
Both Alembic's documentation & Pytest-Alembic's documentation say that async migrations should be run by configuring your env like this:
async def run_migrations_online() -> None:
"""Run migrations in 'online' mode.
In this scenario we need to create an Engine
and associate a connection with the context.
"""
connectable = engine
async with connectable.connect() as connection:
await connection.run_sync(do_run_migrations)
await connectable.dispose()
asyncio.run(run_migrations_online())
but this doesn't resolve the issue (however it does work for production migrations outside of pytest).
I stumpled upon a library called pytest-alembic that provides some built-in tests for this.
When running pytest --test-alembic, I get the following exception:
got Future attached to a different loop
A few comments on pytest-asyncio's GitHub repository suggest that the following fixture might fix it:
#pytest.fixture(scope="session")
def event_loop() -> Generator:
loop = asyncio.get_event_loop_policy().new_event_loop()
yield loop
loop.close()
but it doesn't (same exception remains).
Next I tried to run the upgrade test manually, using:
async def test_migrations(alembic_runner):
alembic_runner.migrate_up_to("revision_tag_here")
which gives me
alembic_runner.migrate_up_to("revision_tag_here")
venv/lib/python3.9/site-packages/pytest_alembic/runner.py:264: in run_connection_task
return asyncio.run(run(engine))
RuntimeError: asyncio.run() cannot be called from a running event loop
However this is an internal call by pytest-alembic, I'm not calling asyncio.run() myself, so I can't apply any of the online fixes for this (try-catching to check if there is an existing event loop to use, etc.). I'm sure this isn't related to my own asyncio.run() defined in the alembic env, because if I add a breakpoint - or just raise an exception above it - the line is actually never executed.
Lastly, I've also tried nest-asyncio.apply(), which just hangs forever.
A few more blog posts suggest to use this fixture to initialize database tables for tests:
async with engine.begin() as connection:
await connection.run_sync(Base.metadata.create_all)
which works for the purpose of creating a database to run tests against, but this doesn't run through the migrations so that doesn't help my case.
I feel like I've tried everything there is & visited every docs page, but I've got no luck so far. Running an async migration test surely can't be this difficult?
If any extra info is required I'm happy to provide it.
I got this up and running pretty easily with the following
env.py - the main idea here is that the migration can be run synchronously
import asyncio
from logging.config import fileConfig
from alembic import context
from sqlalchemy import engine_from_config
from sqlalchemy import pool
from sqlalchemy.ext.asyncio import AsyncEngine
config = context.config
if config.config_file_name is not None:
fileConfig(config.config_file_name)
target_metadata = mymodel.Base.metadata
def run_migrations_online():
connectable = context.config.attributes.get("connection", None)
if connectable is None:
connectable = AsyncEngine(
engine_from_config(
context.config.get_section(context.config.config_ini_section),
prefix="sqlalchemy.",
poolclass=pool.NullPool,
future=True
)
)
if isinstance(connectable, AsyncEngine):
asyncio.run(run_async_migrations(connectable))
else:
do_run_migrations(connectable)
async def run_async_migrations(connectable):
async with connectable.connect() as connection:
await connection.run_sync(do_run_migrations)
await connectable.dispose()
def do_run_migrations(connection):
context.configure(
connection=connection,
target_metadata=target_metadata,
compare_type=True,
)
with context.begin_transaction():
context.run_migrations()
run_migrations_online()
then I added a simple db init script
init_db.py
from alembic import command
from alembic.config import Config
from sqlalchemy.ext.asyncio import create_async_engine
__config_path__ = "/path/to/alembic.ini"
__migration_path__ = "/path/to/folder/with/env.py"
cfg = Config(__config_path__)
cfg.set_main_option("script_location", __migration_path__)
async def migrate_db(conn_url: str):
async_engine = create_async_engine(conn_url, echo=True)
async with async_engine.begin() as conn:
await conn.run_sync(__execute_upgrade)
def __execute_upgrade(connection):
cfg.attributes["connection"] = connection
command.upgrade(cfg, "head")
then your pytest fixture can look like this
conftest.py
...
#pytest_asyncio.fixture(autouse=True)
async def migrate():
await migrate_db(conn_url)
yield
...
Note: I don't scope my migrate fixture to the test session, I tend to drop and migrate after each test.
Related
I'm creating a FastAPI project that integrates with the Django ORM. When running pytest though, the PostgreSQL database is not rolling back the transactions. Switching to SQLite, the SQLite database is not clearing the transactions, but it is tearing down the db (probably because SQLite uses in-memory db). I believe pytest-django is not calling the rollback method to clear the database.
In my pytest.ini, I have the --reuse-db flag on.
Here's the repo: https://github.com/Andrew-Chen-Wang/fastapi-django-orm which includes pytest-django and pytest-asyncio If anyone's done this with flask, that would help too.
Assuming you have PostgreSQL:
Steps to reproduce:
sh bin/create_db.sh which creates a new database called testorm
pip install -r requirements/local.txt
pytest tests/
The test is calling a view that creates a new record in the database tables and tests whether there is an increment in the number of rows in the table:
# In app/core/api/a_view.py
#router.get("/hello")
async def hello():
await User.objects.acreate(name="random")
return {"message": f"Hello World, count: {await User.objects.acount()}"}
# In tests/conftest.py
import pytest
from httpx import AsyncClient
from app.main import fast
#pytest.fixture()
def client() -> AsyncClient:
return AsyncClient(app=fast, base_url="http://test")
# In tests/test_default.py
async def test_get_hello_view(client):
"""Tests whether the view can use a Django model"""
old_count = await User.objects.acount()
assert old_count == 0
async with client as ac:
response = await ac.get("/hello")
assert response.status_code == 200
new_count = await User.objects.acount()
assert new_count == 1
assert response.json() == {"message": "Hello World, count: 1"}
async def test_clears_database_after_test(client):
"""Testing whether Django clears the database"""
await test_get_hello_view(client)
The first test case passes but the second doesn't. If you re-run pytest, the first test case also starts not passing because the test database is not clearing the transaction from the first run.
I adjusted the test to not include the client call, but it seems like pytest-django is simply not creating a transaction around the Django ORM, because the db is not being cleared for each test:
async def test_get_hello_view(client):
"""Tests whether the view can use a Django model"""
old_count = await User.objects.acount()
assert old_count == 0
await User.objects.acreate(name="test")
new_count = await User.objects.acount()
assert new_count == 1
async def test_clears_database_after_test(client):
"""Testing whether Django clears the database"""
await test_get_hello_view(client)
How should I clear the database for each test case?
Turns out my pytest.mark.django_db just needed transaction=True in it like pytest.mark.django_db(transaction=True)
I'm trying to populate my db with some data and to do so I'm making migrations in which I need to run async uploader that fetch files, parse it to SQLModel and insert to db with SQLAlchemy.
I've initialized alembic as async and my env file is looks like official template from here:
https://github.com/sqlalchemy/alembic/blob/main/alembic/templates/async/env.py
Right now my migrations looks like:
def upload_func():
loop = asyncio.new_event_loop()
try:
return loop.run_until_complete(upload_coro())
finally:
loop.close()
def upgrade():
with ThreadPoolExecutor(max_workers=1) as executor:
future = executor.submit(upload_func)
future.result()
But it runs ok on first migration and fails on every second migration when it comes to await self.session.execute(stmt) with:
RuntimeError: Task <Task pending coro=<upload_coro() running at /backend/src/alembic/versions/upload_smth.py:32> cb=[_run_until_complete_cb() at /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/base_events.py:157]> got Future attached to a different loop
So I need do re-run alembic upgrade head multiple times.
What am I doing wrong?
How to get rid of that "Future attached to a different loop"?
Is there any proper way to run coroutines with SQLAlchemy deep down from alembic sync upgrade() function?
Solved down below.
When you are using async env.py template at https://github.com/sqlalchemy/alembic/blob/main/alembic/templates/async/env.py, which establishes SQLAlchemy's async "greenlet context" around everything that's running, you can run coroutines as:
from sqlalchemy.util import await_only
def upgrade():
await_only(my_coroutine())
I have also asked this question on behave GitHub discussions and SQLAlchemy GitHub discussions.
I am trying to hookup a SQLAlchemy 1.4 engine and global scoped asynchronous session in behave before_all and before_scenario hooks to model testing similar to that outlined in the following blog article
The approach is to have a parent transaction and each test running in a nested transaction that gets rolled back when the test completes.
Unfortunately the before_all, before_scenario hooks are synchronous.
The application under test uses an asynchronous engine and asynchronous session created using sessionmaker:
def _create_session_factory(engine) -> sessionmaker[AsyncSession]:
factory = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
factory.configure(bind=engine)
return factory
In the before_scenario test hook the following line raises an error when I try to create a scoped session.
"""THIS RAISES AN ERROR RuntimeError: no running event loop"""
context.session = context.Session(bind=context.connection, loop=loop)
The full code listing for setting up the test environment is listed below.
How do I get an asynchronous scoped session created in the synchronous before_all, before_scenario test hooks of behave?
import asyncio
import logging
from behave.api.async_step import use_or_create_async_context
from behave.log_capture import capture
from behave.runner import Context
from behave.model import Scenario
from sqlalchemy import event
from sqlalchemy.ext.asyncio import AsyncSession, async_scoped_session
from sqlalchemy.ext.asyncio.engine import async_engine_from_config
from sqlalchemy.orm.session import sessionmaker
from fastapi_graphql.server.config import Settings
logger = logging.getLogger()
#capture(level=logging.INFO)
def before_all(context: Context) -> None:
"""Setup database engine and session factory."""
logging.info("Setting up logging for behave tests...")
context.config.setup_logging()
logging.info("Setting up async context...")
use_or_create_async_context(context)
loop = context.async_context.loop
asyncio.set_event_loop(loop)
logging.info("Configuring db engine...")
settings = Settings()
config = settings.dict()
config["sqlalchemy_url"] = settings.db_url
engine = async_engine_from_config(config, prefix="sqlalchemy_")
logging.info(f"Db engine configured for connecting to: {settings.db_url}")
logging.info("Creating a global session instance")
factory = sessionmaker(bind=engine, class_=AsyncSession, expire_on_commit=False)
# factory.configure(bind=engine)
Session = async_scoped_session(factory(), scopefunc=asyncio.current_task)
context.engine = engine
context.connection = loop.run_until_complete(engine.connect())
context.factory = factory
context.Session = Session
#capture(level=logging.INFO)
def after_all(context: Context) -> None:
"""Teardown database engine gracefully."""
loop = context.async_context.loop
logging.info("Closing connection")
loop.run_until_complete(context.connection.close())
logging.info("Closing database engine...")
loop.run_until_complete(context.engine.dispose())
logging.info("Database engine closed")
#capture(level=logging.INFO)
def before_scenario(context: Context, scenario: Scenario) -> None:
"""Create a database session."""
loop = context.async_context.loop
logging.info("Starting a transaction...")
context.transaction = loop.run_until_complete(context.connection.begin())
logging.info("Transaction started...")
logging.info("Creating a db session...")
breakpoint()
# THIS RAISES AN ERROR RuntimeError: no running event loop
context.session = context.Session(bind=context.connection, loop=loop)
logging.info("Db session created")
breakpoint()
logging.info("Starting a nested transaction...")
context.session.begin_nested()
logging.info("Nested transaction started...")
#event.listens_for(context.session, "after_transaction_end")
def restart_savepoint(db_session, transaction):
"""Support tests with rollbacks.
This is required for tests that call some services that issue
rollbacks in try-except blocks.
With this event the Session always runs all operations within
the scope of a SAVEPOINT, which is established at the start of
each transaction, so that tests can also rollback the
“transaction” as well while still remaining in the scope of a
larger “transaction” that’s never committed.
"""
if context.transaction.nested and not context.transaction._parent.nested:
# ensure that state is expired the way session.commit() at
# the top level normally does
context.session.expire_all()
context.session.begin_nested()
#capture(level=logging.INFO)
def after_scenario(context: Context, scenario: Scenario) -> None:
"""Close the database session."""
logging.info("Closing db session...")
loop = asyncio.get_event_loop()
loop.run_until_complete(context.Session.remove())
logging.info("Db session closed")
logging.info("Rolling back transaction...")
loop.run_until_complete(context.transaction.rollback())
logging.info("Rolled back transaction")
I have a FastAPI application where I have several tests written with pytest.
Two particular tests are causing me issues. test_a calls a post endpoint that creates a new entry into the database. test_b gets these entries. test_b is including the created entry from test_a. This is not desired behaviour.
When I run the test individually (using VS Code's testing tab) it runs fine. However when running all the tests together and test_a runs before test_b, test_b fails.
My conftest.py looks like this:
import pytest
from fastapi.testclient import TestClient
from sqlmodel import Session, SQLModel, create_engine
from application.core.config import get_database_uri
from application.core.db import get_db
from application.main import app
#pytest.fixture(scope="module", name="engine")
def fixture_engine():
engine = create_engine(
get_database_uri(uri="postgresql://user:secret#localhost:5432/mydb")
)
SQLModel.metadata.create_all(bind=engine)
yield engine
SQLModel.metadata.drop_all(bind=engine)
#pytest.fixture(scope="function", name="db")
def fixture_db(engine):
connection = engine.connect()
transaction = connection.begin()
session = Session(bind=connection)
yield session
session.close()
transaction.rollback()
connection.close()
#pytest.fixture(scope="function", name="client")
def fixture_client(db):
app.dependency_overrides[get_db] = lambda: db
with TestClient(app) as client:
yield client
The file containing test_a and test_b also has a module-scoped pytest fixture that seeds the data using the engine fixture:
#pytest.fixture(scope="module", autouse=True)
def seed(engine):
connection = test_db_engine.connect()
seed_data_session = Session(bind=connection)
seed_data(seed_data_session)
yield
seed_data_session.rollback()
All tests use the client fixture, like so:
def test_a(client):
...
SQLAlchemy version is 1.4.41, FastAPI version is 0.78.0, and pytest version is 7.1.3.
My Observations
It seems the reason tests run fine on their own is due to SQLModel.metadata.drop_all(bind=engine) being called at the end of testing. However I would like to avoid having to do this, and instead only use rollback between tests.
What worked really well for me is using testcontainers: https://github.com/testcontainers/testcontainers-python.
#pytest.fixture(scope="module", name="session_for_db_in_testcontainer")
def db_engine():
"""
Creates testcontainer with Postgres db
"""
pg_container = PostgresContainer('postgres:latest')
pg_container.start()
# Fireup the SQLModel engine with the uri of the container
db_engine = create_engine(pg_container.get_connection_url())
sqlmodel_metadata.create_all(db_engine)
with Session(db_engine) as session_for_db_in_testcontainer:
# add some rows to start, for test get requests and posting existing data
add_data_to_test_db(database_input_path, session_for_db_in_testcontainer)
yield session_for_db_in_testcontainer
# Will be executed after the last test
session_for_db_in_testcontainer.close()
pg_container.stop()
Like this during the test run a (Postgres) DB is created it only runs during a session, module or function depending on the scope of the fixture. If you want, you can add test data to the db as well like in the example.
In your case you might want to set the scope of this fixture as function. Than test_a and test_b should run independently.
I'm trying to mimic Django behavior when running tests on FastAPI: I want to create a test database in the beginning of each test, and destroy it in the end. The problem is the async nature of FastAPI is breaking everything. When I did a sanity check and turned everything synchronous, everything worked beautifully. When I try to run things async though, everything breaks. Here's what I have at the moment:
The fixture:
#pytest.fixture(scope="session")
def event_loop():
return asyncio.get_event_loop()
#pytest.fixture(scope="session")
async def session():
sync_test_db = "postgresql://postgres:postgres#postgres:5432/test"
if not database_exists(sync_test_db):
create_database(sync_test_db)
async_test_db = "postgresql+asyncpg://postgres:postgres#postgres:5432/test"
engine = create_async_engine(url=async_test_db, echo=True, future=True)
async with engine.begin() as conn:
await conn.run_sync(SQLModel.metadata.create_all)
Session = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
async with Session() as session:
def get_session_override():
return session
app.dependency_overrides[get_session] = get_session_override
yield session
drop_database(sync_test_db)
The test:
class TestSomething:
#pytest.mark.asyncio
async def test_create_something(self, session):
data = {"some": "data"}
response = client.post(
"/", json=data
)
assert response.ok
results = await session.execute(select(Something)) # <- This line fails
assert len(results.all()) == 1
The error:
E sqlalchemy.exc.PendingRollbackError: This Session's transaction has been rolled back due to a previous exception during flush. To begin a new transaction with this Session, first issue Session.rollback(). Original exception was: Task <Task pending name='anyio.from_thread.BlockingPortal._call_func' coro=<BlockingPortal._call_func() running at /usr/local/lib/python3.9/site-packages/anyio/from_thread.py:187> cb=[TaskGroup._spawn.<locals>.task_done() at /usr/local/lib/python3.9/site-packages/anyio/_backends/_asyncio.py:629]> got Future <Future pending cb=[Protocol._on_waiter_completed()]> attached to a different loop (Background on this error at: https://sqlalche.me/e/14/7s2a)
/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/session.py:601: PendingRollbackError
Any ideas what I might be doing wrong?
Check if other statements in your test-cases involving the database might fail before this error is raised.
For me the PendingRollbackError was caused by an InsertionError that was raised by a prior test.
All my tests were (async) unit tests that involved database insertions into a postgres database.
After the tests, the database session was supposed to do a rollback of its entries.
The InsertionError was caused by Insertions to the database that failed a unique constraint. All subsequent tests raised the PendingRollbackError.