How to configure pytest in FastAPI?

Question

I'm trying to write some tests for my FastAPI -application. I have defined app in main.py like this: app = FastAPI(). I try to import this in my test test_api.py:

from fastapi.testclient import TestClient
from main import app

client = TestClient(app)

def test_read_main():
  # test code

When I run the tests I get these errors:

E   pydantic.error_wrappers.ValidationError: 4 validation errors for Settings
E   SERVER_NAME
E     field required (type=value_error.missing)
E   SERVER_HOST
E     field required (type=value_error.missing)
E   PROJECT_NAME
E     field required (type=value_error.missing)
E   DATABASE_URL
E     field required (type=value_error.missing)

How should I configure the tests so I could run them successfully?

Edit. This is the structure of the app.

project
│   .env
│  
│
└───app
    │  
    │ 
    |───app
    |   │ main.py
    |   │
    |   |___config
    |           config.py
    | 
    |
    |───tests
         test_file01.py

Answer 1

You need to define the environment vars in test,

import os
from fastapi.testclient import TestClient

os.environ['SERVER_NAME'] = 'server_name'
os.environ['SERVER_HOST'] = 'server_host'
os.environ['PROJECT_NAME'] = 'project_name'
os.environ['DATABASE_URL'] = 'DATABASE_URL'

from main import app
client = TestClient(app)

def test_read_main():
  # test code

The app import needs to be after the env var definition, it's better to set your application as fixture.