Andrew Seaford

In this article, we are going to explore how to unit test a simple restful endpoint using Python 3 and the modules Flask, Flask_restx, and UnitTest. The test will focus on testing an endpoint that has a parameter for specifying the name of the required setting.

Creating The Application

First, we are going to create a simple flask application, the application will host a GET endpoint called /Setting/{sname} that returns the value for a single setting.

• Create a text file called endPointGet.py and add the following code.

from flask import Flask
from flask_restx import Resource, Api
from flask_cors import CORS

app = Flask(__name__)
CORS(app)  # Allow CORS for all routes
api = Api(app, version='1.0', title='EndPoint Get', description='Example Restful Service')

mySettingsData = [
            {'Name': 'Setting1', 'Value': 'Value1'},
            {'Name': 'Setting2', 'Value': 'Value2'}
        ]

def getSettingValue(sname):
    for setting in mySettingsData:
        if setting['Name'] == sname:
            return setting['Value']
    return None

@api.route('/Settings', doc={"description": "Get all settings"})
class GetSettings(Resource):
    def get(self):
        return mySettingsData

@api.route('/Setting/<string:sname>', doc={"description": "Get one setting value"})
@api.param('sname', 'Setting Name')
class GetSetting(Resource):
    def get(self, sname):
        value = getSettingValue(sname)
        if value == None:
            return {'message': f'Invalid setting name. {sname} does not exist'}, 400
        else:
            return value

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5500, debug=False)

Running The Application

To run the application:

• From the terminal execute the python file.
  python endPointGet.py

• Open a web browser and navigate to http://127.0.0.1:5500, the page will show the swagger document for the Flask application.
  

• Click default to expand the list of endpoints
  

• Click the GET button next to /Setting/{sname}.
  

• Click the Try it out button.
  

• Enter the name of the setting into sname and then click the Execute button.
  

• The value of the setting will be displayed in the Response Body
  

• Entering a setting name that does not exist will result in an error code 400.
  

Unit Testing The Application

The unit test will test two scenarios when the setting name exists and when the setting name does not exist. To unit test the flask application:

• Create a text file called endPointGetTests.py and add the following code

import unittest
import json
from endPointGet import *

class SystemSettingsTestCase(unittest.TestCase):
    def setUp(self):
        """Set up for unit tests, function is executed before tests begin"""

        self.client = app.test_client()
        app.config['TESTING'] = True

    def test_get_setting(self):
        """Test confirms that GET /Setting/{sname} will return a setting value"""

        # Arrange
        expected_result = 'Value1'

        # Act
        response = self.client.get('/Setting/Setting1') # Make a GET request to the /Setting/{sname} endpoint

        # Assert
        self.assertEqual(response.status_code, 200) # Check that the response status code is 200 OK
        actual_result = json.loads(response.data) # Parse the JSON response
        self.assertEqual(actual_result, expected_result) # Check that the response contains the expected data

    def test_get_setting_bad_setting_name(self):
        """Test confirms that GET /Setting/{sname} will return 400 when the setting name does not exisit"""

        # Arrange
        sname = 'Bad_Setting_Name'
        expected_message = f'Invalid setting name. {sname} does not exist'

        # Act
        response = self.client.get(f'/Setting/{sname}') # Make a GET request to the /Settings endpoint

        # Assert
        self.assertEqual(response.status_code, 400) # Check that the response status code is 400 BAD
        self.assertEqual(response.status, '400 BAD REQUEST') # Check the response status message        
        response_json = response.get_json() # Extract the JSON data from the response    
        self.assertIn('message', response_json) # Ensure the 'message' key is in the response
        self.assertEqual(response_json['message'], expected_message) # Check that the response message contains the expected message

if __name__ == '__main__':
    unittest.main()

• To run the test, execute the Python file endPointGetTests.py from the terminal.

python endPointGetTests.py

• The log messages from a successful test will end with OK.