---
canonical: "https://www.jsolly.com/blog/two-weird-reasons-I-love-unit-tests/"
title: "Unit Tests as a Design Tool: Increase Coverage and Improve Your Code"
description: "Discover how unit tests can be a design tool to improve your code and increase coverage. Learn how to fix multiple bugs without re-running your code."
author: "John Solly"
published: "2022-05-13T03:11:06.000Z"
updated: "2022-05-13T03:11:06.000Z"
---

<a id="unit-tests-as-a-design-tool-increase-coverage-and-improve-your-code"></a>

# Unit Tests as a Design Tool: Increase Coverage and Improve Your Code

![Unit, Acceptance, UI test pyramid.](https://d1d7p8ufhgz4ld.cloudfront.net/media/post_metaimgs/testingPyramid.png)

The benefits of using unit tests in your code cannot be overstated. Not only do they serve as a powerful refactoring tool, but they also act as a design tool to improve the quality of your code. If your application currently lacks unit tests, now is the time to start the journey toward [100% unit test coverage](https://www.jsolly.com/blog/how-to-get-100-percent-unit-test-coverage/).

<a id="unit-tests-as-a-refactoring-tool"></a>

## Unit tests as a refactoring tool

Without unit tests, refactoring can be a tedious process. It typically involves attempting to run or compile your code, reading a single stack trace, and fixing a single bug. With unit tests, however, this process becomes much more efficient. When multiple unit tests fail, you can fix multiple bugs simultaneously, saving you significant time.

<a id="unit-tests-as-a-design-tool"></a>

## Unit tests as a design tool

To convince you further**,** learn about why [integration tests are a scam](https://www.jsolly.com/blog/integration-tests-are-a-scam-i-wrote-them-anyway/) and why you should write unit tests instead. Another favorite reason I love unit tests is that they are a fabulous design tool.

> It's difficult to write simple tests for complicated code.
> 
> \- John Solly

In addition to their usefulness as a refactoring tool, unit tests also serve as an excellent design tool. Writing simple tests for complicated code can be difficult, so the implementation probably has room for improvement. I [followed the TDD approach for my blog "blogthedata.com"](https://www.jsolly.com/blog/test-strategy-no-existing-tests/) and found missing coverage across several files. 

<pre><code class="language-python">Name                                    Stmts   Miss  Cover   Missing
---------------------------------------------------------------------
blog/templates/blog/categories.html        42      2    95%   35-36
blog/templates/blog/home.html              47     19    60%   33-52
blog/templates/blog/search_posts.html      50     19    62%   36-55
blog/templates/blog/user_posts.html        37     19    49%   20-39
---------------------------------------------------------------------
TOTAL                                    1164     59    95%</code></pre>

I discovered that I had duplicated the same pagination code across multiple files in my application. Rather than writing separate tests for the same logic in various locations, I chose to refactor the code by moving it into a separate file and utilizing [Django's {% include %} tag](https://docs.djangoproject.com/en/4.0/ref/templates/builtins/) to inherit it into the four templates.

By taking this approach, I achieved 100% code coverage after re-running my tests, without having to write a single additional test. This is a great example of how unit tests can be used as a design tool to improve the quality of your code and make it more maintainable.

May 13, 2022 in [Dev Tools](https://www.jsolly.com/blog/category/dev-tools/)

Updated May 13, 2022