Why Is Unit Testing So Hard and Why Can You Do About It

I’ve seen many codebases in my years of experience as a developer.

Some were neatly organized, some were so chaotic that it was hard to understand what the code sometimes did.

But there’s one thing the best codebases had in common: unit tests. Unit testing is a practice that helps you detect bugs early and make sure your source code works correctly before putting it into production. It’s hard to argue that writing tests for your code are not worth the effort. But when deadlines are tight, it feels like an impossible task to write all the unit tests you want.

So why is unit testing so hard? In most cases, it’s not easy to write thorough unit tests. That’s because writing unit tests requires:

  • in-depth knowledge of the project in which you’re working,
  • testable code,
  • test-friendly architecture,
  • a plan for testing.

This article covers why unit tests are challenging and gives tips to make them easier.

Is unit testing hard to learn?

It depends on the person, but you can probably pick it up within two weeks. The basics of unit testing are not hard to grasp and master.

Unit testing is a process of validating that the smallest building blocks in an application work correctly. Some of these building blocks are independent of the context in which they’re used. Therefore, a unit test is only concerned with the correctness of a specific unit of code.

unit testing

This is what makes unit testing so valuable. Unit tests are fast to write and easy to read. They can be written by anybody on the team and executed by anybody else.

Unit tests are a safety net built to catch bugs before they reach production. If a test fails, it means that something has changed, and you need to go back and fix it.

It’s not hard to learn unit testing:

  • The hard part is to make sure you write tests for all the possible scenarios, which will give you 100% confidence in your deployed codebase.
  • The hard part comes when the existing code is not suitable for covering with unit testing. That kind of code is called legacy code.

Why is unit testing so hard?

Let’s take a closer look at what are the different elements that can make unit testing a hard effort.

Unit testing requires in-depth knowledge of the project in which you’re working

Unit tests are a great way to ensure that the changes and additions you make to your code don’t break anything else. But, being a white box software testing technique, unit testing is an in-depth process that requires a lot of knowledge about the code and how it interacts with other parts of the project. As a result, it can be hard to start writing unit tests, especially if you are new to the codebase. The trap you can easily fall into is to write bad unit tests that test the implementation detail instead of observable behavior.

The good news is that it’s possible to overcome these challenges and reap the benefits of unit testing with the proper guidance and resources.

Unit tests benefit your project, but they also improve your development skills by requiring you to think about how you will use your code in different situations and contexts. Understanding these situations will help you write better code for the future.

Unit testing requires testable code

Unit testing is a valuable technique that all software developers should utilize to write testable code. However, you can’t test all code due to its nature.

There are different types of code. For example, some classes are small and contain short methods that have simple logic. On the other hand, some code is only functional after the application is deployed to the cloud, where it talks to the database and other services.

Unit testing makes it easier to test logic, while integration testing tests the interaction across multiple components. As a result, unit tests are faster than integration tests, but integration tests cover application interaction with external services.

Unit testing requires test-friendly architecture

Unit testing also requires a test-friendly architecture. What does that mean?

A test-friendly architecture is an architecture that uses dependency injection. Dependency injection means that your code has a list of dependencies (other classes and libraries) that it needs to use. Still, instead of hard-coding these dependencies into the class, you use a dependency injection container to provide these dependencies at runtime.

The benefit of dependency injection is that you can easily replace dependencies with test doubles (a fake implementation of the dependency), making it possible to test the code without using the actual dependencies.

For example, if your code uses the Twitter API, you can use a mock object for the Twitter API client instead of using the actual Twitter API. This allows you to write test code that doesn’t require an Internet connection or a live Twitter account.

Unit testing requires a plan for testing

Unit testing is a crucial step for any developer to take to ensure his code works correctly. Therefore, the developer must be mindful of the tests he is running and create a plan for testing. It is also imperative to plan out what tests will be used before beginning development to achieve better test coverage.

When writing your tests, it is essential to ensure that you are approaching your code from the context on the front end. This means ensuring that any code you are writing fulfills the user’s need. In other words, test the observable behavior, don’t test the implementation details.

Also, you need to be aware that some code can’t be covered with unit tests. You need to follow the testing pyramid principle and have other layers of testing:

  • Integration tests cover a more extensive module in your code.
  • UI testing interacts with your application through the UI layer.

A good testing plan also includes a continuous integration system that will run the whole test suite on every pushed commit.

How to make unit testing easier?

There are a couple of things you can do to make the process easier:

  1. You can start writing unit tests for parts of the code base that you are familiar with. For example, if you know that a class has a specific method that you use heavily in your project, it’s worth writing a unit test for this method and making sure that it works as expected.
  2. When working on new features or bug fixes in the codebase, try to write unit tests for them too. This will help you understand how the code works and how other developers should use it.
  3. Test driven development (TDD) is an agile software development technique that relies on repeating a concise development cycle. You turn a requirements into a very simple test, then write just enough code to pass the failing test, with refactoring as the final step.
  4. Finally, when working with legacy code, try to write characterization tests for it. They will make the code easier to maintain, and the tests can be a valuable source of information on how the developer should use the code.

What happens if you only test your code manually?

If you never write automated tests and only perform manual testing, you will have to remember how the code works. If you change the code and something breaks, you will need to figure out what happened and how to fix it.

How easy is it to remember how the code works? Not very easy. Even if you are a fast learner and can quickly understand new things, it still takes time to memorize the paths through the codebase and all of its dependencies.

Also, when working on a project for a long time, it’s easy for your memory to get fuzzy. You might not even know that something has changed in the codebase until someone reports a bug. When you write unit tests, you document the code and make it easier to understand. The tests also clearly indicate whether the code works, so there is no need to remember how it works.

Why do many developers hate to write unit tests?

Unit testing is a necessary component of agile programming. Unit testing can be a valuable tool for debugging and analysis, and it’s a way to ensure that your code won’t have any unintended consequences.

People often hate writing unit tests because they take a lot of time and can be repetitive to write. Still, it’s a valuable investment that yields valuable results. The unit testing ensures code stability and lessens the chances of introducing bugs into the code later. In this way, it can be a valuable investment.

Is unit testing worth the time?

Unit testing can require a lot of work, but the time and effort you put into unit testing will be a springboard for testing different code levels when you develop more software.

Unit tests will be a significant asset if you work on a long-term project. They allow you to build upon the production code you’ve already written. And give you some indicator or idea of whether the code you build breaks the existing code.


Unit testing is hard because it deals with things at a very granular level. It puts your code under the microscope and forces you to test in tiny increments.

Unit testing shines by allowing you to work on a section of code, then check its validity, and then, as soon as you change anything in your code, it tells you if you’re breaking other parts of the program. This will allow you to support every part of your app and enable you to progress your project while minimizing the number of new bugs.

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