Writing Unit Tests for REST API in Python

A little background: over the last few months, I have been contributing in open source organization , where I’m working on a project called . It is a badge generator with a simple web UI to add data and generate printable badges in PDF. FOSSASIA BadgeYaY back-end is now shifted to and to test functions used in REST-API, we need some testing technology which will test each and every function used in the API. For our purposes, we chose the popular Python test suite. Badgeyay REST-API unit tests In this blog, I’ll be discussing how I have written unit tests to test REST-API. Badgeyay First, let’s understand what is unit tests and why we have chosen it. Then we will move onto writing API tests for . These tests have a generic structure and thus the code I mention would work in other REST API testing scenarios, often with little to no modifications. Badgeyay Let’s get started and understand API testing step by step. What is Unit tests? Unit tests is a Python unit testing framework which supports test automation, sharing of setup and shutdown code for tests, aggregation of tests into collections, and independence of the tests from the reporting framework. The module provides classes that make it easy to support these qualities for a set of tests. unit test Why Unit tests? We get two primary benefits from unit testing, with a majority of the value going to the first: Guides your design to be loosely coupled and well fleshed out. If doing test driven development, it limits the code you write to only what is needed and helps you to evolve that code in small steps. Provides fast automated regression for re-factors and small changes to the code. Unit testing also gives you living documentation about how small pieces of the system work. We should always strive to write comprehensive tests that cover the working code pretty well. Now, here is glimpse of how I wrote unit tests for testing code in the REST-API back-end of . Using unit tests python package and modules, we can test REST API in test automation. Badgeyay requests Below is the code snippet for which I have written unit tests in one of my pull requests. def output(response_type, message, download_link):if download_link == ‘’:response = [{‘type’: response_type,‘message’: message}]else:response = [{‘type’: response_type,‘message’: message,‘download_link’: download_link}]return jsonify({‘response’: response}) To test this function, I basically created a mock object which could simulate the behavior of real objects in a controlled way, so in this case a mock object may simulate the behavior of the output function and return like an JSON response without hitting the real REST API. Now the next challenge is to parse the JSON response and feed the specific value of the response JSON to the Python automation script. So Python reads the JSON as a dictionary object and it really simplifies the way JSON needs to be parsed and used. something And here’s the content of the file. backend/tests/test_basic.py #!/usr/bin/env python3 “””Tests for Basic Functions”””import sysimport jsonimport unittest sys.path.append(“../..”)from app.main import * class TestFunctions(unittest.TestCase):“””Test case for the client methods.”””def setup(self):app.app.config[‘TESTING’] = Trueself.app = app.app.test_client()# Test of Output function def test\_output(self): with app.test\_request\_context(): # mock object out = output(‘error’, ‘Test Error’, ‘local\_host’) # Passing the mock object response = \[ { ‘type’: ‘error’, ‘message’: ‘Test Error’, ‘download\_link’: ‘local\_host’ } \] data = json.loads(out.get\_data(as\_text=True) # Assert response self.assertEqual(data\[‘response’\], response) if __name__ == ‘__main__’:unittest.main() And finally, we can verify that everything works by running . nosetests Screen-shot of Test Passing This is how I wrote unit tests in repository. BadgeYaY With that, I have reached the end of our discussion on writing Unit Tests for REST API in Python Web Application. I wrote this post as a solution to this in BadgeYaY project. If you liked this post, consider having a look at my other work on 🙂. issue GitHub Sources : Unit testing framework Did you like the read? Medium doesn’t offer partner program in my country―so I ask people to buy me coffee instead.