How do you set up a Flask application with SQLAlchemy for testing?

Question

It seems common practice in Flask to start like this:

from flask import Flask
from flaskext.sqlalchemy import SQLAlchemy
app = Flask(__name__)
SQLALCHEMY_DAT         


        

Answer 1

Your instinct to use environment variables is correct. However, there is some danger of running unit tests with the wrong db. Also, you may not want to connect_db with every request and everywhere you want to use db. You can use a config directory and environment variables which you set explicitly. This is the best I've come up with so far.

run.py
shell.py

config/__init__.py
config/test.py
config/postgres.py
...

main/__init__.py
main/someapp/__init__.py
main/someapp/models.py

...
main/tests/__init__.py
main/tests/testutils.py

so, the config files may be:

# config/test.py
SQLALCHEMY_DATABASE_URI = "sqlite://"

and

# config/postgres.py
SQLALCHEMY_DATABASE_URI = 'postgresql://user:pw@localhost/somedb'

So, I can explicitly set the db in my base TestCase:

import os
from flask.ext.testing import TestCase

os.environ["DIAG_CONFIG_MODULE"] = "config.test"
from main import app, db


class SQLAlchemyTest(TestCase):

    def create_app(self):
        return app

    def setUp(self):
        db.create_all()

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

Then, the main/__init__.py, for me:

import os

from flask import Flask, render_template, g
from flask.ext.sqlalchemy import SQLAlchemy

# by default, let's use a DB we don't care about
# but, we can override if we want
config_obj = os.environ.get("DIAG_CONFIG_MODULE", "config.test")
app = Flask(__name__)
app.config.from_object(config_obj)
db = SQLAlchemy(app)

@app.before_request
def before_request():
    g.db = db
    g.app = app

# ...
@app.route('/', methods=['GET'])
def get():
    return render_template('home.html')
# ...    
from main.someapp.api import mod as someappmod
app.register_blueprint(someappmod)

Then, in the other files, where I know what config I want to run, potentially:

# run.py
import os
os.environ["DIAG_CONFIG_MODULE"] = "config.postgres"
from main import app
app.run(debug=True)

and

# shell.py
import os
os.environ["DIAG_CONFIG_MODULE"] = "config.postgres"

from main import app, db
from main.symdiag.models import *
from main.auth.models import *
print sorted(k for k in locals().keys() if not k.startswith("_"))
import IPython
IPython.embed()

Maybe .. best so far :P.