How to implement pytest for FastAPI with MongoDB(Motor) - mongodb

Question

I want to write tests for my FastAPI endpoints
example for my code:
from fastapi import FastAPI
from fastapi.testclient import TestClient
app = FastAPI()
#app.get("/todos")
async def get_todo_by_title(title: str,current_user: User = Depends(get_current_user))
document = await collection.find_one({"title": title})
return document
client = TestClient(app)
def test_get_todo_by_title():
response = client.get("/todos")
assert response.status_code == 200
What the best way to test my endpoints?
I want to use fake DB for testing, something like json file
db = {
todos: [...]
}

Answer 1

It is not the best option to use fake data from a JSON file. Instead, you can use a testing DB (based on the env you are running your app through), or any other DB (dev, stg, ..etc), and delete your test data after running all unit tests.
Here is how to simply apply the latter approach in FastAPI;
Assume you have 3 simple tables (or collections) X, Y, and Z
MongoDB is the DB service
PyTest is the test engine
conftest.py
from pytest import fixture
from starlette.config import environ
from starlette.testclient import TestClient
from config.db_connection import database, X_collection, Y_collection, Z_collection
#fixture(scope="session")
def test_X():
return {
"_id": "10",
"name": "test",
"description": "test",
"type": "single value",
"crt_at": "2022-06-27T12:23:15.143Z",
"upd_at": "2022-06-27T12:23:15.143Z"
}
//test_Y and test_Z fixtures should be like test_X
#fixture(scope="session", autouse=True)
def test_client(test_X, test_Y, test_Z):
import main
application = main.app
with TestClient(application) as test_client:
yield test_client
db = database
//Here, delete any objects you have created for your tests
db[X_collection].delete_one({"_id": test_X["_id"]})
db[Y_collection].delete_one({"_id": test_Y["_id"]})
db[Z_collection].delete_one({"_id": test_Z["_id"]})
environ['TESTING'] = 'TRUE'
Unit tests should look like the following sample.
test_X_endpoints.py
def test_create_X(test_client, test_X):
response = test_client.post("/create_X_URI/", json=test_X)
assert response.status_code == 201
//Add assertions as needed
def test_list_X(test_client):
response = test_client.get("/list_X_objects_URI/?page=1&size=1")
assert response.status_code == 200
//Add assertions as needed