1. Introduction

1.1 Tutorial's Goal

In this tutorial, we will learn how to test and secure APIs using Django REST Framework (DRF). The primary focus will be on understanding various testing strategies, incorporating authentication, and applying permissions to secure your API.

1.2 Learning Outcomes

By the end of this tutorial, you will be able to:
- Write tests for your APIs
- Implement authentication in your APIs
- Apply permissions to your APIs

1.3 Prerequisites

To make the most out of this tutorial, you should have:
- Basic knowledge of Python
- Familiarity with Django and Django REST Framework
- A local development environment set up for Python and Django

2. Step-by-Step Guide

2.1 Testing APIs

Testing is a critical part of any application development process. Here, we'll use Django's built-in testing framework to test our APIs.

2.1.1 Writing a test

This involves creating a test class that inherits from Django’s TestCase class. For an API, we would create test methods that make HTTP requests to the API using a test client and then check the response.

2.1.2 Running the tests

To run the tests, we use Django's test runner. This can be activated by running python manage.py test from the command line.

2.2 Securing APIs

Securing APIs involves implementing authentication and permissions.

2.2.1 Authentication

Authentication is about verifying the identity of the users. DRF provides several methods for authentication like Basic Authentication, Token Authentication, Session Authentication, etc.

2.2.2 Permissions

Once the user is authenticated, permissions determine whether a request should be granted or denied. DRF provides various permission classes like AllowAny, IsAuthenticated, IsAdminUser, IsAuthenticatedOrReadOnly, etc.

3. Code Examples

3.1 Testing APIs

from django.test import TestCase
from django.urls import reverse
from rest_framework.test import APIClient
from .models import CustomModel

class ModelTestCase(TestCase):
    """This class defines the test suite for the CustomModel model."""

    def setUp(self):
        self.client = APIClient()
        self.model_data = {'name': 'Test'}
        self.response = self.client.post(
            reverse('model_create'),
            self.model_data,
            format="json"
        )

    def test_api_can_create_a_model(self):
        """Test the api has model creation capability."""
        self.assertEqual(self.response.status_code, 201)

In this example, we first import the necessary modules and classes. We then create a test case for our model. In the setUp method, we initialize our test client and our test data, and we make a POST request to our API. In the test_api_can_create_a_model method, we check that the response status code is 201, indicating a successful creation of an object.

3.2 Securing APIs

from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView

class HelloWorldView(APIView):
    permission_classes = (IsAuthenticated,)

    def get(self, request):
        return Response({"message": "Hello, World!"})

In this example, we import the necessary classes. We then create a view for our API. We set the permission classes to IsAuthenticated, which means only authenticated users can access this view. If a non-authenticated user tries to access this view, they will receive a 403 Forbidden response.

4. Summary

In this tutorial, we covered how to test and secure your APIs using Django REST Framework. We learned how to write and run tests, and how to implement authentication and permissions in your APIs.

4.1 Next Steps

Continue learning more about DRF's features like throttling, pagination, versioning, etc. Also, learn more about different types of testing like unit testing, integration testing, and end-to-end testing.

4.2 Additional Resources

• Django REST Framework official documentation: https://www.django-rest-framework.org/
• Django official documentation for testing: https://docs.djangoproject.com/en/3.2/topics/testing/

5. Practice Exercises

5.1 Exercise 1

Write a test case for a GET request to the HelloWorldView.

5.2 Exercise 2

Update the HelloWorldView to only allow GET requests from admin users.

5.3 Exercise 3

Write a test case for a POST request to the HelloWorldView.

5.4 Solutions

# Solution for Exercise 1
def test_api_can_get_hello_world(self):
    response = self.client.get(reverse('hello_world'))
    self.assertEqual(response.status_code, 200)
    self.assertEqual(response.data, {"message": "Hello, World!"})

# Solution for Exercise 2
# Update the HelloWorldView
class HelloWorldView(APIView):
    permission_classes = (IsAdminUser,)

    def get(self, request):
        return Response({"message": "Hello, World!"})

# Solution for Exercise 3
def test_api_cannot_post_hello_world(self):
    response = self.client.post(reverse('hello_world'))
    self.assertEqual(response.status_code, 405)  # 405 means Method Not Allowed

Remember to keep practicing and trying different types of tests, authentication, and permissions. Happy coding!