[Python] Unable to fix ModuleNotFoundError in Flask despite proper convention

My Flask backend directory structure looks like this:

backend/
├── app/
│ ├── __init__.py
│ ├── routes/
│ │ ├── dev_routes.py
│ │ └── ...
│ └── models.py
├── tests/
│ ├── __init__.py
│ └── routes/
│ └── test_dev_routes.py
└── main.py
|__ ...



I'm trying to run my test_dev_routes.py file via the command pytest tests/routes when I'm in my backend folder in my terminal. I keep facing this error:

_______ ERROR collecting tests/routes/test_dev_routes.py ________
ImportError while importing test module '/Users/name/folder/project-name/project/backend/tests/routes/test_dev_routes.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
../../../../miniconda3/lib/python3.10/importlib/__init__.py:126: in import_module
return _bootstrap._gcd_import(name[level:], package, level)
tests/routes/test_dev_routes.py:3: in <module>
from app.routes import dev_routes
E ModuleNotFoundError: No module named 'app'


This is what the test_dev_routes.py file looks like:

import pytest
from flask import Flask, json
from app.routes import dev_routes
from app import create_app, db
from app.models import User, Doctor, Slot, Queue, QueueEntry

@pytest.fixture
def client():
app = Flask(__name__)
app.register_blueprint(dev_routes.api, url_prefix='/api/dev')
app.config['TESTING'] = True
with app.test_client() as client:
with app.app_context():
db.create_all() # Create the database tables
yield client
with app.app_context():
db.drop_all() # Clean up after tests


My dev_routes.py file contains this api = Blueprint('dev_api', __name__) and it works properly when I retrieve this api variable from other files when I'm inside the app folder. I also tried moving my tests/routes folder into app and I still faced the same error. I don't understand what I'm doing wrong.

The __init__.py file in my app folder looks like this:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_cors import CORS

db = SQLAlchemy()
_app_instance = None # Singleton instance

def create_app(config_name: str = None):
global _app_instance
if _app_instance is None:
_app_instance = Flask(__name__)
_app_instance.config.from_object('config.Test')
db.init_app(_app_instance)
CORS(_app_instance)
return _app_instance


I tried setting the Pythonpath: export PYTHONPATH=$(pwd)/backend, and this didn't work.

I tried moving my entire tests folder into my app folder and that still didn't work.

I tried doing something like importing backend.app.routes wherein I put a __init__.py file in my backend folder, that still didn't work.

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