when you follow the book FlaskWeb developer to Chapter 7 to adjust the project structure, there is a UserWarning: Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set warning using flask_sqlalchemy
this is the config.py code

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
import os
app = Flask(__name__)

basedir = os.path.abspath(os.path.dirname(__file__))

class Config:
    app.config["SECRET_KEY"] = "hard to guess string"
    app.config["MAIL_DEFAULT_SENDER"] = "123@qq.com"  -sharp 
    app.config["SECRET_KEY"] = "hard to guess string"
    app.config["SQLALCHEMY_DATABASE_URI"] = "mysql+pymysql://root:430202@127.0.0.1:3306/test1"
    app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = True
    app.config["SQLALCHEMY_COMMIT_ON_TEARDOWN"] = True


    app.config["FLASKY_ADMIN"] = "123@123.cn"

    @staticmethod
    def init_app(app):
        pass

class DevelopmentConfig(Config):
    DEBUG = True
    app.config["MAIL_SERVER"] = "smtp.qq.com"
    app.config["MAIL_PORT"] = 587
    app.config["MAIL_USE_TLS"] = True
    app.config["MAIL_USERNAME"] = "123@qq.com"
    app.config["MAIL_PASSWORD"] = "ddjogvrpawyebcdi"
    app.config["SQLALCHEMY_DATABASE_URI"] = "mysql+pymysql://root:430202@127.0.0.1:3306/test1"
    app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = True
    app.config["SQLALCHEMY_COMMIT_ON_TEARDOWN"] = True


class TestingConfig(Config):
    TESTING = True
    app.config["SQLALCHEMY_DATABASE_URI"] = "mysql+pymysql://root:430202@127.0.0.1:3306/test1"


class ProductionConfig(Config):
    app.config["SQLALCHEMY_DATABASE_URI"] = "mysql+pymysql://root:430202@127.0.0.1:3306/test1"


config = {
    "development": DevelopmentConfig,
    "testing": TestingConfig,
    "production": ProductionConfig,
    "default": DevelopmentConfig

}

this is the app__init__.py code

from flask import Flask, render_template
from flask_bootstrap import Bootstrap
from flask_mail import Mail
from flask_moment import Moment
from flask_sqlalchemy import SQLAlchemy
from config import config
from flask_login import LoginManager

bootstrap = Bootstrap()
mail = Mail()
moment = Moment()
db = SQLAlchemy()
login_manager=LoginManager()
login_manager.session_protection="strong"
login_manager.login_view="auth.login"


def create_app(config_name):
    app = Flask(__name__)
    app.config.from_object(config[config_name])
    config[config_name].init_app(app)
    bootstrap.init_app(app)
    mail.init_app(app)
    moment.init_app(app)
    db.init_app(app)
    login_manager.init_app(app)

    from .main import main as main_blueprint
    app.register_blueprint(main_blueprint)

    from .auth import auth as auth_blueprint
    app.register_blueprint(auth_blueprint,url_prefix="/auth")

-sharp 

    return app

this is the test file

import unittest
from flask import current_app
from app import create_app, db


class BasicsTestCase(unittest.TestCase):
    def setUp(self):
        self.app = create_app("testing")
        self.app_context = self.app.app_context()
        self.app_context.push()
        db.create_all()
    def tearDown(self):
        db.session.remove()
        db.drop_all()
        self.app_context.pop()

    def test_app_exists(self):
        self.assertFalse(current_app is None)

    def test_app_is_testing(self):
        self.assertTrue(current_app.config["TESTING"])

the error message when running python manage.py test is as follows:
br > UserWarning: Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. UsersDELLPycharmProjectsbookvenvlibsitelypackagesflaskchemistry Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:/:memory:".
"Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set."
test_app_exists (test_basic.BasicsTestCase). CJV UsersDELLPycharmProjectsbookvenvenvlibsitelypackagesflaskexamples sqlalchemicalchemicals initability.pyRom 774: UserWarning: Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:/:memory:".
"Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set."
have tried all the solutions that have similar problems on the Internet, but still haven"t solved them. I really don"t know what the problem is. Can anyone take a look at it?