How to properly mock AuthJWT (or any other injected dependencies)

[dmsfabiano]

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Example Code

from typing import Dict

from fastapi import FastAPI, HTTPException, Depends, Request
from fastapi.responses import JSONResponse
from fastapi_jwt_auth import AuthJWT
from fastapi_jwt_auth.exceptions import AuthJWTException

from ml_api.api.mongo.user import UserLayer

app = FastAPI()
user_db = UserLayer()


@AuthJWT.load_config
def get_config():
    return AuthSettings(



@app.post('/get_tokens')
def get_tokens(user: User, Authorize: AuthJWT = Depends()):
    if not user_db.is_valid_user(user.username, user.password):
        raise HTTPException(status_code=401, detail="Bad username or password")

    return {"access_token": Authorize.create_access_token(subject=user.username),
            "refresh_token": Authorize.create_refresh_token(subject=user.username)}

# ---------------- test -------------------------------

import asyncio
import sys
from unittest.mock import MagicMock

from fastapi.testclient import TestClient
from fastapi_jwt_auth import AuthJWT
from pytest import fixture

from ml_api.api.main import app


@fixture(scope='function')
def test_client():
    if sys.platform == "win32" and sys.version_info >= (3, 8, 0):
        asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
    app.dependency_overrides[AuthJWT] = MagicMock()
    return TestClient(app)

@fixture(scope='function')
def test_authorize_mock(test_client):
    return test_client.app.dependency_overrides[AuthJWT]

@fixture(scope='package')
def test_get_tokes_request():
    return {
        "username": "test_username",
        "password": "test_password"
    }

class TestGetTokens:
    def test_on_valid_user(self, mocker, test_client, test_get_tokes_request, test_authorize_mock):
        user_db_mock = mocker.patch(f"{BASE_PATH}.user_db")
        user_db_mock.is_valid_user.return_value = True

        response = test_client.post('/get_tokens', json=test_get_tokes_request)

        assert_that(response.status_code, is_(equal_to(HTTPStatus.OK)))
        assert_that(response.json(), is_(equal_to({
            "access_token": test_authorize_mock.create_access_token.return_value,
            "refresh_token": test_authorize_mock.create_refresh_token.return_value
        })))
        user_db_mock.is_valid_user.assert_called_once_with(
            test_get_tokes_request["username"],
            test_get_tokes_request["password"]
        )

Description

• I am trying to successfully mock AuthJWT, so that instead of executing the external depencies of it (.create_access_token for example) I can use MagicMock to simply validate that the functiosn themselves are being called
• When the pytest test runs, I expect it to return 200, and the test to pass
• However, the test fails with 422 with an error of "field missing, value error", Even though that the the correct request is being sent to the Starlette test client
• I suspect mocking AuthJWT through the dependency_overrides may be causing some internal issues with the Dependency injection, making FastAPI think the endpoint requires more parameters

I am sure I missed something, or did something incorrectly, so I am mainly looking for any hints or the right way to do it!

Operating System

Windows

Operating System Details

No response

FastAPI Version

0.78.0

Python Version

3.8.0

Additional Context

No response

[JarroVGIT]

Please see this issue for solution and explanation https://github.com/tiangolo/fastapi/issues/3331

[dmsfabiano]

That is super helpful @JarroVGIT - Thank you ! Even though that this allows me to succesfuly mock AuthJWT, it does not quite allow me to control or manipulate the return of the mock

def test_client(test_authorize_mock):
    if sys.platform == "win32" and sys.version_info >= (3, 8, 0):
        asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
    app.dependency_overrides[AuthJWT] = lambda: test_authorize_mock
    return TestClient(app)

@fixture(scope='function')
def test_authorize_mock():
    return MagicMock()

regardless of how I manipulate test_authorize_mock the response from the endpoint it's always

{
    "access_token": {},
    "refresh_token" {}
}

instead of

{
    "access_token": "",
    "refresh_token": ""
}

even if I explicitly do this on my test

test_authorize_mock.create_access_token.return_value = ""

[JarroVGIT]

I am sorry for not being more helpful but I have limited experience myself with MagicMock(). I wouldn't know how to manipulate it for your test cases, I just remembered the issue I mentioned and why MagicMock() caused some issues there, but anything else is above my level of knowledge.