FastAPI: Pydantic's BaseSettings injection for pytest

There are a few options how to change app config for tests. According to FastAPI docs, it's recommended to use `dependency_overrides`, but there might be a case where we need to change the entire app settings (using Pydantic's BaseSettings here).

config.py

[...code ommited...]

settings = Settings()  # Read from environment


@lru_cache()
def get_config() -> Settings:
    """Return cached settings object.

    Returns:
        Settings object.
    """

    return settings

conftest.py

Import module and some settings to be injected

import app.config as conf
from app.config import settings, Settings, Postgres, Bucket0

Create new configuration obejct(s)

# Change database settings for testing. This will ensure, that
# tests won't be run with the default database settings.
# If needed, this can be overridden in .env.test file which has
# a higher precedence.

test_database = Postgres(
    host="postgres",  # docker-compose
    port=5432,
    username="testuser",
    password="testpassword",
    database_name="testdb",
)

# As for now, Google doesn't offer local emulator for the Cloud Storage Bucket.
test_bucket = Bucket0(name="test_bucket")

Override Settings() with TestSettings()

class TestSettings(Settings):
    postgres = test_database
    bucket0 = test_bucket

    class Config:
        """Pydantic configuration meta-class."""

        env_file = ".env.test"

Re-assign the "settings" variable within conf file with TestSettings

conf.settings = TestSettings()

Import app -> TestClinet(app)

# IMPORTANT: Import has to happen after "app.config.settings" has been re-assigned with TestSettings()
from app.main import app  # noqa

daaniam/example.md