Testing a Flask REST API using Factory Boy and an in-memory sqlite database
I’m developing a REST API using Python’s Flask microframework. As I wanted to do test driven development to ensure good test coverage, I needed a working testing framework. After checking out a few different options, I found one that works well for my use case. I thought I’d share my setup in case it may be of help to others.
First, this is how I create the server:
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# File: server/server.py import connexion from database import db def create_app(config): connexion_app = connexion.FlaskApp(__name__) # For stock Flask users, use something like "app <span class="pl-k">=</span> Flask(<span class="pl-c1">__name__</span>)" instead connexion_app.add_api('api.yaml', strict_validation=True) app = connexion_app.app app.config['SQLALCHEMY_DATABASE_URI'] = config.get_database_uri() app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False db.init_app(app) return app |
Note that the function parameter is an object that contain a function name “get_database_uri”. By doing it this way, we’ll have control over which database our server will be using. For testing, we’ll pass an object with an “get_database_uri” function that return “sqlite:///:memory:”. For production, the “get_database_uri” will return connection info for a real database.
Next, the database module::
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# File: server/database.py from flask_sqlalchemy import SQLAlchemy db = SQLAlchemy() |
To run the application, something like this would suffice:
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# File: server/__init__.py from server import create_app app = create_app() app.run() |
Now, for the interesting part. The setup below create a server with an in-memory sqlite database backend. This means that our tests will run using an in-memory database, which is both really fast and easy. We’ll use Factory Boy for populating the database with test data. I’m using the flask_testing extension, and the code is based on it’s documentation. Here’s the test code:
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# File: server/tests/test_users.py from flask_testing import TestCase from server import create_app from server.database import db from models.user import user as user_model import factory class MyTest(TestCase): TESTING = True def get_database_uri(self): return 'sqlite:///:memory:' def create_app(self): # pass in test configuration return create_app(self) def setUp(self): db.create_all() def tearDown(self): db.session.remove() db.drop_all() class UserFactory(factory.alchemy.SQLAlchemyModelFactory): class Meta: model = user_model name = "John Doe" # Default name class UsersTests(MyTest): def _create_user(self, *args, **kwargs): user = UserFactory.build(**kwargs) db.session.add(user) db.session.commit() return user def test_that_correct_users_are_returned_from_the_endpoint(self): self._create_user(name="Mike Stern") self._create_user(name="John Scofield") response = self.client.get("/api/users") # Check that the response contain the two users we created above |