Flask Special Topics ==================== Writing Unit Tests for Flask ---------------------------- There are several different approaches for writing *unit tests* for Flask apps, some of which are included in the Flask documentation. One approach which is most congruent with the topics we already covered in this class, is to instead write *integration tests*. For these tests, the key thing is that you have to have an actual copy of your Flask server running. Then, the tests will perform requests.get() to the various routes and you can evaluate the output. Be careful to make sure that your tests are independent of the data, which may change over time. The job of these unit tests is not to check / validate that the right data is being returned; rather, the goal is to make sure the routes work and return the right kind of response. If your code also has standalone functions separate from the functions decorated as Flask routes, (e.g., you may have written helper functions inside of your file that are not routes but help process or retrieve data), then you would still want to import those and test them as normal in your unit test file. Consider the previous code we made for getting degrees with different HTTP requests. .. code-block:: python3 :linenos: from flask import Flask from flask import request data = [ {'id': 0, 'year': 1990, 'degrees': 5818}, {'id': 1, 'year': 1991, 'degrees': 5725}, {'id': 2, 'year': 1992, 'degrees': 6005}, {'id': 3, 'year': 1993, 'degrees': 6123}, {'id': 4, 'year': 1994, 'degrees': 6096} ] app = Flask(__name__) @app.route('/degrees', methods=['GET', 'DELETE']) def degrees(): global data if request.method == 'GET': return(data) elif request.method == 'DELETE': content = request.get_json() new_data = [] for item in data: if item['id'] != content['id']: new_data.append(item) data = new_data return(data) @app.route('/degrees/', methods=['GET']) def degrees_for_id(id): for x in data: if x['id'] == id: return x return f"Error: ID {id} not found." @app.route('/degrees//degrees', methods=['GET']) def only_degrees_for_id(id): for x in data: if x['id'] == id: return {'id' : id, 'degrees': x['degrees'] } return f"Error: ID {id} not found." if __name__ == '__main__': app.run(debug=True, host='0.0.0.0') Look at the following pytest snippet that tests the /degrees and /degrees/ routes: .. code-block:: python3 :linenos: import requests import logging def test_degrees_route(): response1 = requests.get('http://127.0.0.1:5000/degrees') logging.debug(f"Response from /degrees: {response1.json()}") assert response1.status_code == 200 assert isinstance(response1.json(), list) == True assert len(response1.json()) == 5 assert response1.json()[0]['id'] == 0 assert response1.json()[0]['year'] == 1990 assert response1.json()[0]['degrees'] == 5818 assert response1.json()[1]['id'] == 1 assert response1.json()[1]['year'] == 1991 assert response1.json()[1]['degrees'] == 5725 def test_specific_degree_route(): response2 = requests.get('http://127.0.0.1:5000/degrees/' + str(1)) assert response2.status_code == 200 assert isinstance(response2.json(), dict) == True assert len(response2.json()) == 3 assert response2.json()['id'] == 1 assert response2.json()['year'] == 1991 assert response2.json()['degrees'] == 5725 These lines may need to be modified depending on the format of data returned by your API. And, as mentioned above, it assumes these tests are performed when your API is already running. Reverse Proxy with ``ngrok`` ---------------------------- Up to now, our Flask apps have been isolated to their host hardware. What if we want to access our Flask apps from outside our host hardware? A utility called ``ngrok`` can be used to provide a reverse proxy on the fly. .. note:: To do this, you need an ngrok account and access token, which can be obtained `here `_ First, install ``ngrok`` by following this `tutorial `_ once your account is created and setup. Confirm ``ngrok`` is working and add your `access token `_: .. code-block:: console [terminal]$ ngrok --help NAME: ngrok - tunnel local ports to public URLs and inspect traffic ... [terminal]$ ngrok config add-authtoken Authtoken saved to configuration file: /home/ubuntu/.config/ngrok/ngrok.yml Assuming you have a Flask app running on ``localhost`` and port ``5000``, then do the following: .. code-block:: console [terminal]$ ngrok http http://localhost:5000 This will lock your terminal into an interface that looks like the following: .. code-block:: console ngrok Policy Management Examples http://ngrok.com/apigwexamples Session Status online Account andrew solis (Plan: Free) Update update available (version 3.18.2, Ctrl-U to update) Version 3.17.0 Region United States (us) Latency 34ms Web Interface http://127.0.0.1:4040 Forwarding https://022d-136-62-4-166.ngrok-free.app -> http://localhost:5000 Connections ttl opn rt1 rt5 p50 p90 0 0 0.00 0.00 0.00 0.00 Navigate to or curl the link provided to access your Flask app from outside your system. Press ``Ctrl+C`` to quit forwarding. Flask and HTML -------------- Flask has the ability to render HTML templates that contain a mix of static data and variables (for run-time dynamic data). The route you write will take the template from a predefined location, inject any variables, and render it into a final HTML document to return to the client. In your Flask project directory, create a folder called ``templates`` and add the following HTML document as ``example.html``. It uses Jinja syntax for injecting dynamic data (``{{name}}``): .. code-block:: html Flask Templating Example

Hello, {{name}}!

This file should be stored in the "templates" folder as "example.html"

Then, adapt the ``/`` Flask route to return that HTML document using Flask's ``render_template()`` method. The old version of the route which returns a plain string is also provided as reference. .. code-block:: python3 :linenos: from flask import Flask, render_template app = Flask(__name__) @app.route('/', methods=['GET']) def hello_name(name): return render_template('example.html', name=name) ### For reference, this is the / route without render_template # @app.route('/', methods=['GET']) # def hello_name(name): # return f'Hello, {name}!\n' if __name__ == '__main__': app.run(debug=True, host='0.0.0.0') Additional Resources -------------------- * `Ngrok `_ * `Flask Templates `_