What's the one of the most important and often overlooked parts of software applications from web applications, mobile applications to Cloud Native application? Unit tests of course! Unit tests are an integral part of any software application because they allow for the detection of bug/defects, improve maintainability of code and aid in regression testing when making updating existing code-bases.
Figure 1: Diagram detailing the unit testing process!
In this blog post, we will show you guys how to write basic unit test using Pytest for Django applications so without further ado, let's jump right in!
To begin unit testing with Pytest we will need the
pip package manager installed. If you don't have
pip installed then refer to this article by opensource.com on how to do so.
pip installed, we can install
pytest via the following command:
pip install -U pytest
Then as a sanity check, running the following command to see the version of
pytest that was installed:
Next we'll need a sample python application to run our basic unit tests on. If you don't have one, feel free to clone this simple blog application here, as this is the application to be used in this blog post.
Then, make sure to activate a virtual environment when in the root folder of this project by running the following command:
python -m venv virtual_env
As the previous command created the virtual environment folder, we now have to activate it using this command:
source virtual_env/Scripts/activate # for Windows users source virtual_env/bin/activate # for Linux and Mac users
Great! You're now in a Python virtual environment. Moving on to the testing section...
To begin let's start out by creating a 'tests' folder in the root folder. After this, let's create a file called
conftest.py inside the newly created 'tests' folder.
When beginning the unit testing process it is important to have a file to hold configuration data. When a single file holds the logic for configuring the unit tests, we enforce the DRY principle by reducing code and logic duplication.
conftest.py file, let's add the following code:
import pytest import factory from pytest_factoryboy import register from rest_framework.test import APIClient, APIRequestFactory from django.contrib.auth import get_user_model from forum.models import ForumUser from django.contrib.auth.hashers import make_password from django import VERSION as DJANGO_VERSION from django.test import TestCase from django.urls import reverse class ConfTest(TestCase): @pytest.mark.django_db def test_register_success(self): superuser = User.objects.create_superuser( username="admin", email="email@example.com", password="admin" ) superuser.save() assert User.objects.count() > 0 @pytest.mark.django_db def create_test_user(self): test_user = User.objects.create( username="test_user", email="test_user@test_user.com", password="test_user" ) test_user.save() return test_user
Here's an explanation of the what we just added:
test_register_success(): First we create a superuser(to learn more about Django superusers read this article) and persist that user to the database. Then we query the database for that user using the assert statement
assert User.objects.count() > 0, which proves that the newly created superuser is saved to the database successfully
create_test_user(): This function is used to create a new
Userinstances whenever the need arises to do so. For example when persisting a
Userinstance is required for it's
authorfield, therefore using this function to get an
Useris a good use of the DRY principle(to learn more about the DRY Principle click here)
Next, let's move on to testing the models in this application. To do so, first create a new file inside the
tests folder called
model_test.py then add the following code to it:
import pytest from django.contrib.auth.models import User from django.test import TestCase from blogapp.models import Category, Post from conftest import ConfTest class ModelTest(TestCase): @pytest.mark.django_db def test_category_model_persists(self): new_category = Category() new_category.name = "new_category" new_category.save() assert new_category.name == "new_category" assert Category.objects.count() > 0 @pytest.mark.django_db def test_post_model_persists(self): new_post = Post() new_post.title = "new_post" new_post.author = ConfTest.create_test_user(self) old_post_obj_count = Post.objects.filter().count() new_post.save() new_post_obj_count = Post.objects.filter().count() assert new_post.title == "new_post" assert old_post_obj_count < new_post_obj_count
Now for a breif explanation as to what we have just added:
test_category_model_persists(self): This test case is for testing the ability of the Category class to save instances of itself
test_post_model_persists(self): This test case is similar to the one above with the addition of having to create an User object, as the
authorfield requires a foreign key of type User(to learn more about foreign keys click here)
Now let's move on to doing some basic unit testing for the routing in the application.
First, start out be creating a new file in the
tests folder called
routes_test.py. Then populate it with the following code:
import pytest from django.contrib.auth.models import User from django.test import TestCase from blogapp.models import Category, Post from django.urls import reverse class RouteTest(TestCase): @pytest.mark.django_db def test_homepage(self): homepage_url = reverse("blog:MainView") response = self.client.get(homepage_url) assert response.status_code == 200 assert response.context["request"].path == "/" @pytest.mark.django_db def test_no_access_page(self): no_access_url = reverse("blog:NoAccess") response = self.client.get(no_access_url) assert response.status_code == 200 assert response.context["request"].path == "/noaccess/"
Now for an explanation of what we just added:
test_homepage(): Tests whether we are able to navigate to the homepage upon going to the route: "/". Notice that the function
reverse()is used to provide much of the same functionality as the well known
url()method, in that it acts as a generator and alias for urls defined in the
config/routes.pyfile(for more info on the reverse() function check out it's Django documentation page)
test_no_access_page(): Very similar to the
test_homepage()test cases, with the exception of testing
Finally, let's add one more set of unit tests for the
Post objects in the
models.py file. Let's start by creating a new file called
test_post.py in the
tests folder. After that just add the following code to our newly created
import pytest from django.contrib.auth.models import User from django.test import TestCase from blogapp.models import Category, Post from django.db.utils import IntegrityError from conftest import ConfTest class PostTest(TestCase): @pytest.mark.django_db def test_post_saves_when_author_present(self): new_post = Post() new_post.author = ConfTest.create_test_user(self) new_post.save() Post.objects.count() > 0 @pytest.mark.django_db def test_post_not_save_when_author_empty(self): new_post = Post() with self.assertRaises(IntegrityError): new_post.save() @pytest.mark.django_db def test_new_post_has_zero_likes_after_saved(self): new_post = Post() new_post.author = ConfTest.create_test_user(self) new_post.save() assert new_post.likes == 0
Now for an explanation of we just added:
test_post_saves_when_author_present(): This unit test primarily tests whether instances of the
Postclass can be saved when including a value for it's
test_post_not_save_when_author_empty(): This unit test contrasts the one above in that the
authorfield is intentionally left blank in order to trigger an
IntegerityError. The assertion contained in this unit test expects this
IntegerityErrorto be thrown when attempting to save the
test_new_post_has_zero_likes_after_saved(): This unit tests is similar to the one above with the slight twist of checking whether the
likesfield has a default value of
Postinstance object is persisted with a blank
Now that we're done adding all our basic unit tests, let's run these test cases!
To do this just run the following command:
And voila! Here are the test results showing 9 successfully passing test cases:
Figure 2: 9 passing unit tests!✔ ✔ ✔
Congratulations! You now know how to make basic unit tests in your Django applications. If you need access to the source code for this application you can access it by visiting it's GitHub link.
Well that's it for this post! Thanks for following along in this article and if you have any questions or concerns please feel free to post a comment in this post and I will get back to you when I find the time.