Django Testing Tutorial
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Testing is an important but often neglected part of any Django project. In this tutorial we’ll review testing best practices and example code that can be applied to any Django app.
Broadly speaking there are two types of tests you need to run:
- Unit Tests are small, isolated, and focus on one specific function.
- Integration Tests are aimed at mimicking user behavior and combine multiple pieces of code and functionality.
While we might we use a unit test to confirm that the homepage returns an HTTP status code of 200, an integration test might mimic the entire registration flow of a user.
For all tests the expectation is that the result is either expected, unexpected, or an error. An expected result would be a 200 response on the homepage, but we can–and should–also test that the homepage does not return something unexpected, like a 404 response. Anything else would be an error requiring further debugging.
The main focus of testing should be unit tests. You can’t write too many of them. They are far easier to write, read, and debug than integration tests. They are also quite fast to run.
Complete source code is available on Github .
When to run tests
The short answer is all the time! Practically speaking whenever code is pushed or pulled from a repo to a staging environment is ideal. A continuous integration service can perform this automatically. You should also re-run all tests when upgrading software packages, especially Django itself.
Layout
By default all new apps in a Django project come with a tests.py
file. Any test within this file that starts with test_
will be run by Django’s test runner. Make sure all test files start with test_ .
As projects grow in complexity, it’s recommended to delete this initial tests.py
file and replace it with an app-level tests
folder that contains individual tests files for each area of functionality.
For example:
|__app |__tests |-- __init__.py |-- test_forms.py |-- test_models.py |-- test_views.py
Sample Project
Let’s create a small Django project from scratch and thoroughly test it. It will mimic the message board app from Chapter 4 of Django for Beginners .
On the command line run the following commands to start our new project. We’ll place the code in a folder called testy
on the Desktop, but you can locate the code anywhere you choose.
$ cd ~/Desktop $ mkdir testy && cd testy $ pipenv install django $ pipenv shell (testy) $ django-admin startproject myproject . (testy) $ python manage.py startapp pages
Now update settings.py
to add our new pages
app and configure Django to look for a project-level templates
folder.
# myproject/settings.py INSTALLED_APPS = [ 'django.contrib.admin', 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.messages', 'django.contrib.staticfiles', 'pages.apps.PagesConfig', # new ] TEMPLATES = [ ... 'DIRS': [os.path.join(BASE_DIR, 'templates')], # new ... ]
Create our two templates to test for a homepage and about page.
(testy) $ mkdir templates (testy) $ touch templates/home.html (testy) $ touch templates/about.html
Populate the templates with the following simple code.
<!-- templates/home.html --> <h1>Homepage</h1> <!-- templates/about.html --> <h1>About page</h1>
Update the project-level urls.py
file to point to the pages
app.
# myproject/urls.py from django.contrib import admin from django.urls import path, include # new urlpatterns = [ path('admin/', admin.site.urls), path('', include('pages.urls')), # new ]
Create a urls.py
file within the pages
app.
(testy) $ touch pages/urls.py
Then update it as follows:
# pages/urls.py from django.urls import path from .views import HomePageView, AboutPageView urlpatterns = [ path('', HomePageView.as_view(), name='home'), path('about/', AboutPageView.as_view(), name='about'), ]
And as a final step add our views.
# pages/views.py from django.views.generic import TemplateView class HomePageView(TemplateView): template_name = 'home.html' class AboutPageView(TemplateView): template_name = 'about.html'
Start up the local Django server.
(testy) $ python manage.py runserver
Then navigate to the homepage at http://127.0.0.1:8000/ and about page at http://127.0.0.1:8000/about to confirm everything is working.
Time for tests.
SimpleTestCase
Our Django application only has two static pages at the moment. There’s no database involved which means we should use SimpleTestCase .
We can use the existing pages/tests.py
file for our tests for now. Take a look at the code below which adds five tests for our homepage. First we test that it exists and returns a 200
HTTP status code. Then we confirm that it uses the url named home
. We check that the template used is home.html
, the HTML matches what we’ve typed so far, and even test that it does not contain incorrect HTML. It’s always good to test both expected and unexpected behavior.
# pages/tests.py from django.http import HttpRequest from django.test import SimpleTestCase from django.urls import reverse from . import views class HomePageTests(SimpleTestCase): def test_home_page_status_code(self): response = self.client.get('/') self.assertEquals(response.status_code, 200) def test_view_url_by_name(self): response = self.client.get(reverse('home')) self.assertEquals(response.status_code, 200) def test_view_uses_correct_template(self): response = self.client.get(reverse('home')) self.assertEquals(response.status_code, 200) self.assertTemplateUsed(response, 'home.html') def test_home_page_contains_correct_html(self): response = self.client.get('/') self.assertContains(response, '<h1>Homepage</h1>') def test_home_page_does_not_contain_incorrect_html(self): response = self.client.get('/') self.assertNotContains( response, 'Hi there! I should not be on the page.')
Now run the tests.
(testy) $ python manage.py test
They should all pass.
As an exercise, see if you can add a class for AboutPageTests
in this same file. It should have the same five tests but will need to be updated slightly. Run the test runner once complete. The correct code is below so try not to peak…
# pages/tests.py class AboutPageTests(SimpleTestCase): def test_about_page_status_code(self): response = self.client.get('/about/') self.assertEquals(response.status_code, 200) def test_view_url_by_name(self): response = self.client.get(reverse('about')) self.assertEquals(response.status_code, 200) def test_view_uses_correct_template(self): response = self.client.get(reverse('about')) self.assertEquals(response.status_code, 200) self.assertTemplateUsed(response, 'about.html') def test_about_page_contains_correct_html(self): response = self.client.get('/about/') self.assertContains(response, '<h1>About page</h1>') def test_about_page_does_not_contain_incorrect_html(self): response = self.client.get('/') self.assertNotContains( response, 'Hi there! I should not be on the page.')
Message Board app
Now let’s create our message board app so we can try testing out database queries. First create another app called posts
.
(testy) $ python manage.py startapp posts
Add it to our settings.py
file.
# myproject/settings.py INSTALLED_APPS = [ 'django.contrib.admin', 'django.contrib.auth', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.messages', 'django.contrib.staticfiles', 'pages.apps.PagesConfig', 'posts.apps.PostsConfig', # new ]
Then run migrate
to create our initial database.
(testy) $ python manage.py migrate
Now add a basic model.
# posts/models.py from django.db import models class Post(models.Model): text = models.TextField() def __str__(self): """A string representation of the model.""" return self.text
Create a database migration file and activate it.
(testy) $ python manage.py makemigrations posts (testy) $ python manage.py migrate posts
For simplicity we can just a post via the Django admin. So first create a superuser
account and fill in all prompts.
(testy) $ python manage.py createsuperuser
Update our admin.py
file so the posts
app is active in the Django admin.
# posts/admin.py from django.contrib import admin from .models import Post admin.site.register(Post)
Then restart the Django server with python manage.py runserver
and login to the Django admin at http://127.0.0.1:8000/admin/ . You should see the admin’s login screen:
Click on the link for + Add
next to Posts
. Enter in the simple text Hello world!
.
On “save” you’ll see the following page.
Now add our views
file.
# posts/views.py from django.views.generic import ListView from .models import Post class PostPageView(ListView): model = Post template_name = 'posts.html'
Create a posts.html
template file.
(testy) $ touch templates/posts.html
And add the code below to simply output all posts in the database.
<!-- templates/posts.html --> <h1>Message board homepage</h1> <ul> {% for post in object_list %} <li>{{ post.text }}</li> {% endfor %} </ul>
Finally we need to update our urls.py
files. Start with the project-level one.
# myproject/urls.py from django.contrib import admin from django.urls import path, include urlpatterns = [ path('', include('pages.urls')), path('admin/', admin.site.urls), path('posts/', include('posts.urls')), ]
Then create a urls.py
file in the posts
app.
(testy) $ touch posts/urls.py
And populate it as follows.
# posts/urls.py from django.urls import path from .views import PostPageView urlpatterns = [ path('', PostPageView.as_view(), name='posts'), ]
Okay, phew! We’re done. Start up the local server python manage.py runserver
and navigate to our new message board page at http://127.0.0.1:8000/posts .
It simply displays our single post entry. Time for tests!
TestCase
TestCase is the most common class for writing tests in Django. It allows us to mock queries to the database.
Let’s test out our Post
database model.
# posts/tests.py from django.test import TestCase from django.urls import reverse from .models import Post class PostTests(TestCase): def setUp(self): Post.objects.create(text='just a test') def test_text_content(self): post = Post.objects.get(id=1) expected_object_name = f'{post.text}' self.assertEquals(expected_object_name, 'just a test') def test_post_list_view(self): response = self.client.get(reverse('posts')) self.assertEqual(response.status_code, 200) self.assertContains(response, 'just a test') self.assertTemplateUsed(response, 'posts.html')
With TestCase
the Django test runner will create a sample test database just for our tests. Here we’ve populated it with the text 'just a test'
.
In the first test we confirm that the test entry has the primary id of 1
and the content matches. Then in the second test on the view we confirm that that it uses the url name posts
, has a 200 HTTP response status code, contains the correct text, and uses the correct template.
Run the new test to confirm everything works.
(testy) $ python manage.py test
Next Steps
There is far more testing-wise that can be added to a Django project. Most apps feature forms of some kind for GETing and POSTing which should naturally be thoroughly tested.
It’s also a good idea to add testing coverage with coverage.py so you have a rough overview of a project’s total test coverage.
Integration tests are not covered here yet but allow for setting up, using, and then tearing down a live Django server in the background. This can be used to test user authentication flows and so on.
Continuous integration is also a good idea and can be accomplished with a service like Travis CI .
Want to learn more? Here are two book-length treatments on testing that I recommend. I’m also including a lot myself on testing in Django for Professionals.
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