Loader module for flask testing

Loader.py

import json
import os

from sqlalchemy import Table
from app import app, db

class Loader(object):
    """ 
    Reusable class for loading fixture data into test databases.
    """
    # TODO: Accept the app as a param to look up configs
    # TODO: Load JSON files here instead of in the test
    def __init__(self, db, filename):
        self.connection = db.engine.connect()
        self.filename = filename
        self.metadata = db.metadata
        
    def load(self):
        with open(self.filename) as file_in:
            self.data = json.load(file_in)
        return self.load_from_file()

    def load_from_file(self):
        table = Table(self.data[0]['table'], self.metadata)
        self.connection.execute(table.insert(), self.data[0]['records'])
        return

class SomeTest(TestBase):
    def setUp(self) -> None:
        app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite://"
        app.config['TESTING'] = True
        db.create_all()
        
        fixtures = [
            'courses.json',
            'locations.json',
            'roles.json',
            'users.json',
        ]
        
        self.client = app.test_client()

        conn = db.engine.connect()
        metadata = db.metadata

        for filename in fixtures:
            filepath = os.path.join(app.config['FIXTURES_DIR'], filename)
            if os.path.exists(filepath):
                loader = Loader(db, filepath)
                loader.load()
            else:
                raise IOError("Error loading {0}: File could not be found".format(filepath))

    def tearDown(self):
        db.drop_all()
        db.session.close()