FastApi Test Client executing the internal api call - python-unittest

Question

This is the first time I'm trying to write test cases.
I've got a simple FastAPI application and I'm trying to create tests with unittest module.
My goal is to test how app behaves for success case
I've got a simple route in my app:
from fastapi import APIRouter,Request
import requests
router = APIRouter()
#router.post("/demo_router")
async def demo_api(request: Request):
# now calling some private APi's
resp = requests.post("https://example.com", json=data)
return {"resp_data": resp.json()}
Now in my unittest module I'm trying to patch above api. I'm using unittest.mock but I'm getting very strange behavior.
import unittest
from fastapi.testclient import TestClient
from unittest.mock import patch
from main import app
class DemoViewTestCase(unittest.TestCase):
def test_demo_api(self):
with patch('src.endpoints.demo_module.demo_api') as mocked_post:
mocked_post.return_value.status_code = 200
mocked_post.return_value.json = {
"message": "request accepted",
"success": True
}
url = router.url_path_for('demo_api') #fetch the api router
client = TestClient(app)
response = client.post(url, json={"id": "BXBksk8920", "name": "Pjp"})
My problem is TestClient is calling the api and executing it. So it is triggering the internal call "https://example.com" which is causing some execution in the pipelines. So how can I overcome this?
Internal Api shouldn't trigger, I should even mock that? Any solution for that?

Answer 1

When testing all the code will be executed. Thus also the calls to the APIs. If you don't want this, you have to provide mock APIs (postman, mockon and many others provide this).
Because you don't want to be bothered to change the URL's etc when you are testing etc, you could look at automating this.
One way of doing this is to provide all URLs for external APIs using pedantic BaseSettings
config.py:
from pydantic import BaseSettings
class Settings(BaseSettings):
external_api_url: str = "https://api.example.com"
And use this in your code:
settings = Settings() # scans environment for any matching env settings!
...
resp = requests.post(setting.external_api_url, json=data)
In your tests you can override these settings:
settings = Settings(external_api_url="https://mockservice")
This is documented further in Pydantic BaseSettings
There are more way do enhance testing and this is found at the FastAPI documentation:
Dependency Override: https://fastapi.tiangolo.com/advanced/testing-dependencies/
Use different databases for testing: https://fastapi.tiangolo.com/advanced/testing-database/