Why is this route test failing? - docker

Question

I've been following along with the testdriven.io tutorial for setting up a FastAPI with Docker. The first test I've written using PyTest errored out with the following message:
TypeError: Settings(environment='dev', testing=True, database_url=AnyUrl('postgres://postgres:postgres#web-db:5432/web_test', scheme='postgres', user='*****', password='*****', host='web-db',host_type='int_domain', port='5432', path='/web_test')) is not a callable object.
Looking at the picture, you'll notice that the Settings object has a strange form; in particular, its database_url parameter seems to be wrapping a bunch of other parameters like password, port, and path. However, as shown below my Settings class takes a different form.
From config.py:
# ...imports
class Settings(BaseSettings):
environment: str = os.getenv("ENVIRONMENT", "dev")
testing: bool = os.getenv("TESTING", 0)
database_url: AnyUrl = os.environ.get("DATABASE_URL")
#lru_cache()
def get_settings() -> BaseSettings:
log.info("Loading config settings from the environment...")
return Settings()
Then, in the conftest.py module, I've overridden the settings above with the following:
import os
import pytest
from fastapi.testclient import TestClient
from app.main import create_application
from app.config import get_settings, Settings
def get_settings_override():
return Settings(testing=1, database_url=os.environ.get("DATABASE_TEST_URL"))
#pytest.fixture(scope="module")
def test_app():
app = create_application()
app.dependency_overrides[get_settings] = get_settings_override()
with TestClient(app) as test_client:
yield test_client
As for the offending test itself, that looks like the following:
def test_ping(test_app):
response = test_app.get("/ping")
assert response.status_code == 200
assert response.json() == {"environment": "dev", "ping": "pong", "testing": True}
The container is successfully running on my localhost without issue; this leads me to believe that the issue is wholly related to how I've set up the test and its associated config. However, the structure of the error and how database_url is wrapping up all these key-value pairs from docker-compose.yml gives me the sense that my syntax error could be elsewhere.
At this juncture, I'm not sure if the issue has something to do with how I set up test_ping.py, my construction of the settings_override, with the format of my docker-compose.yml file, or something else altogether.
So far, I've tried to fix this issue by reading up on the use of dependency overrides in FastApi, noodling with my indentation in the docker-compose, changing the TestClient from one provided by starlette to that provided by FastAPI, and manually entering testing mode.
Something I noticed when attempting to manually go into testing mode was that the container doesn't want to follow suit. I've tried setting testing to 1 in docker-compose.yml, and testing: bool = True in config.Settings.
I'm new to all of the relevant tech here and bamboozled. What is causing this discrepancy with my test? Any and all insight would be greatly appreciated. If you need to see any other files, or are interested in the package structure, just let me know. Many thanks.

Answer 1

Any dependency override through app.dependency_overrides should provide the function being overridden as the key and the function that should be used instead. In your case you're assigning the correct override, but you're assigning the result of the function as the override, and not the override itself:
app.dependency_overrides[get_settings] = get_settings_override()
.. this should be:
app.dependency_overrides[get_settings] = get_settings_override
The error message shows that FastAPI tried to call your dictionary as a function, something that hints to it expecting a function instead.