Achieving 100% Unit Test Coverage | A Step-by-Step Guide

I made a a commitment 12 days ago to achieve 100% unit test coverage (starting at 0%). Promise, fulfilled!

Curious about unit testing your app?

The first step is to figure out where you stand with current test coverage. Python has an excellent library called coverage that tells you how many statements your tests touch and what is missing. Output looks like this:

The lowest hanging fruit is ensuring routes hook up to the correct View. Here, I’m testing the home route links to the HomeView.

def test_home_url_is_resolved(self):
    self.assertEqual(resolve(self.home_url).func.view_class, HomeView)

After testing routes, move on to Views. For basic Views, you check that a GET results in a 200 (OK) response and the response is using the correct HTML template.

def test_post_detail_view(self):
        response = self.client.get(self.post1_detail_url)
        self.assertEqual(response.status_code, 200)
        self.assertTemplateUsed(response, 'blog/post_detail.html')

The next step is testing Models. We test objects can be created and any methods work as expected. In my case, a Comment associates to a single Post and author. On line 3, we check that the __str__ override method returns Comment content.

def test_comment(self):
        test_comment = Comment.objects.create(post=self.post1, content="I am a comment", author=self.user1)
        self.assertEqual(str(test_comment), "I am a comment")
        self.assertEqual(test_comment.get_absolute_url(), self.post1_detail_url)

Moving on to Forms…Forms are the way Views structure data to be passed into Models, creating new objects. My Post object has 13 attributes. Some are user-provided (content, slug, snippet) whereas others internally generated (likes, views, date posted). 

def test_post_form_valid_data(self):
        form = PostForm(data={
            "title": "My Second Post",
            "slug": "second-post",
            "category": "productivity",
            "metadesc": "I can make you more productive!",
            "draft": False,
            # "metaimg" : ""
            # "metaimg"_mimetype : ""
            "snippet": "Do the things",
            "content": "Do the things. All the things",
            # date_posted : ""
            "author": self.user1
            # "likes"
            # "views"

        })

        self.assertTrue(form.is_valid())

That’s it! My next step is to create integration and acceptance tests. Unlike unit testing, there's no 0-100%. You can write infinite amounts of integration and acceptance tests. 

Until next time!