12 Unit Testing Benefits That Will Blow Your Mind

Software testing is one of the most crucial tools in your developer’s toolkit, but not many people use it. Anyone who claims to be a good programmer is, at the very least, fluent in unit testing. It’s a skill that will make your code better and makes your job easier.

Here are some of the most significant unit testing benefits.

1. Improves code quality

Ever had a nasty bug in your code that’s taken you days to resolve? Did you spend an entire weekend trying to track it down, only to find out it was just a stupid typo?

Enter unit testing.

Unit testing is a functional testing technique that’s been around for years. The main idea is that you write a test method that tests your production code. This helps ensure that any changes you make to the code, the existing features still work correctly.

When you’re writing code without unit tests, you usually have the mindset that “The code is fine. I just didn’t unit test it.” However, writing unit tests doesn’t mean you have to sacrifice code quality. When unit testing code, you’ll get extra quality assurance that you don’t get by doing the regular testing.

unit testing

It’s fairly well known that unit testing can prevent bugs in your code, but it’s not as well known that unit tests can also improve code quality. Developers who take the time to write, execute, and troubleshoot their unit tests are much more likely to be confident in their code, and their confidence will improve the quality of the code itself.

2. Finds bugs early in the process

Unit testing is not a silver bullet. You also need other types of software testing, such as:

  • integration testing
  • system testing
  • performance testing
  • penetration testing
  • exploratory testing

But, unit testing can make a huge difference in releasing quality software. It helps developers avoid critical bugs that are easy to miss and do not surface until later in the development cycle.

As you’re writing your code, there are many times when you might want to test it, but you don’t have much time, or your testing tools are too limited to manually test every line of code to see if it’s working. In these situations, unit testing helps to find bugs early in the process and avoid expensive debugging later in the development cycle. By rerunning tests with the unit testing framework, you can catch regression bugs.

Regression testing is the process of testing a software application to ensure that changes to the code have not introduced new bugs. This process typically includes rerunning existing tests to verify that previously identified bugs have been fixed, as well as running new tests to identify any new bugs that may have been introduced.

By catching bugs early on, the developer doesn’t waste time fixing bugs that would end in production code.

3. Reduces manual testing

As a developer, you probably do a lot of manual testing every time you make some changes. After all, you need to ensure a bug doesn’t make it to your QA.

But, here is a hard truth. Manual testing is no fun. Especially when you’re just not that great at it. But, with the help of unit testing, you can avoid this and increase your productivity with it. It’s one of the most effective ways to improve your code, and you should use it every day.

A testing framework is a great way to automate tests that otherwise would have been manually done. By using the right unit testing tool, and following the right procedure, you can have automated unit testing. This means you don’t have to waste time testing the same code over and over again.

Furthermore, when writing unit tests, you don’t need to worry about how it will behave and don’t have to think about how to test the “case A” with the “case B,” which can be a stressful task for manual testers.

Automated unit tests can keep your code more and more predictable. Automated unit testing helps you to understand the current behavior of the system. It also keeps bugs away from that working behavior.

4. Enables CI/CD process


Continuous integration (CI) and continuous delivery (CD) have become two of the most important software development best practices. Using a CI and CD pipeline, developers can quickly and easily integrate, test, and deploy new code and releases.

However, these processes can have shortcomings. If you don’t have a test suite that covers most of the code, that can lead to various issues. You might face broken builds, endless deployments, or publish a bug to the production.

To combat these issues, it is important to test every single piece of code for the software project. Unit testing is a critical part of the CI/CD process. It helps the development team ensure that changes in the code do not break the existing function of the application.

It is important to write unit tests to find bugs in the code before it is deployed. Test code should be written and run at every stage of the development process and should be a part of the final code review.

Continuous integration and continuous delivery work hand-in-hand with the unit tests. Once you have the pipeline set up, you’ll want to use it to verify that your codebase is always working correctly. Unit testing is a great way to do this: You can use it to test your code in isolation and run it on the continuous integration server.

5. Facilitates changes

Refactoring is a software development practice that aims to improve the readability and maintainability of software by moving code into modules that are easier to understand, test, and modify. It is the process of changing the design of an existing piece of code without changing its external behavior. Refactoring code may involve the removal of code that is no longer needed, the addition of new code, or the modification of existing code in such a way as to improve its quality.

Unit testing supports refactoring by providing a fast feedback loop for verifying that refactoring changes haven’t introduced any bugs.

That means you can go back to your code and refactor it to make it better. If automated tests pass after your changes, this means you haven’t broken anything. With continuous refactoring, you can make your code simpler and simpler. If you make some changes but you make a mistake, you will immediately know. The test runner will tell you with a failing test.

The idea behind unit testing is to create a safety net for developers to change the code and not break anything.

6. Provides living technical documentation

Many developers don’t take full advantage of unit testing benefits. While unit testing can provide multiple benefits to a project, one crucial benefit is often overlooked: they provide up-to-date technical documentation.

Unit tests provide technical documentation about how a code behaves. For example, if you have the following unit tests:

  • Order_cant_be_processed_when_item_is_not_selected
  • Order_cant_be_processed_when_quantity_is_missing
  • Order_cant_be_processed_when_quantity_is_negative
  • Order_cant_be_processed_when_price_is_missing
  • Order_can_be_processed_when_item_and_price_and_quantity_are_positive_numbers

Just by looking at the tests’ names, you can figure out how the application behaves. In this case, the application has validations that the item, quantity, and price fields on order are correctly populated. Only if those conditions are satisfied, the order can be processed. And the last test tells you exactly that.

One important thing to have in mind is that you need to know how to write tests to serve you as useful documentation. You can learn more about creating an awesome name for your test function in the blog post about it.

Technical documentation is important, and integrating it into the development process is a valuable process. However, documentation is the most valuable if you keep it up to date. And unit tests can be that live documentation. As a result, many developers incorporate unit testing into their workflow to produce documentation for the code.

7. Improves software design

Software development is expensive, time-consuming, and prone to failure. It’s one of the most costly and risky things we do. Unit testing is a proven way to improve software design, and it’s a surefire way to slash development costs.

An automated unit test is a great way to ensure that your code is working as intended. However, the code you’re testing can be very abstract and complex. As such, it can be difficult to decipher what the tests are actually trying to test. As a result, the unit test will also have more lines of code if the code under test is not easily testable.

Let me show you what I mean with the following examples:

  1. The class you are testing uses static classes and initializes its own dependencies. In other words, the class doesn’t use dependency injection. Because of that, in the unit test, you need to find various creative ways to provide a stub or mock object to replace the dependencies with the fake implementations. In this case, the test tells you that you need to use dependency injection to improve software design. Better software design leads to more testable code.
  2. Ok, you have started to inject your dependencies. But now, another problem occurs. You have too many dependencies injected through the constructor. As a result, you rely heavily on the mocking framework to fake all dependencies. If your Arrange part of the unit test takes 10-20 lines, then you need to start asking questions about the class under test. And maybe split the class into several smaller classes.

This means that you can think about unit tests as another design tool.

8. Increases code coverage

Code coverage (or test coverage) measures the proportion of an application’s source code that has been executed during testing and is a key consideration for developers when deciding on testing approaches.

Code coverage is a good quality control metric, but writing tests for the sake of code coverage is wrong.

When you write tests to increase the coverage, the tests you produce might not represent the actual business cases. Those tests are here just to increase the number that represents the code coverage. They increase the number of tests in every test class. In addition, they make the unit test suite harder to maintain since there are a lot of tests that are maybe meaningless and cover the path of execution that doesn’t occur in production.

9. Provides the foundation for the testing pyramid

testing pyramid

The testing pyramid is a visual representation of how many different layers of tests you should have in your testing project. It is an idea of dividing your testing efforts into different categories:

  • Unit testing – represents the foundation of the pyramid. It is a white box testing technique. These tests are performed regularly by your development team as part of the development process. The bottom layer is where you write tests that interact with the individual units of your application. You run these tests most frequently since they are fast and you can get immediate feedback.
  • Integration testing – Integration testing is a technique used to test the functionality of a program on all of its components and sub-components. It is a gray box testing technique. Integration test checks if software components are integrated correctly. It also checks that all interactions between those components work as expected. Integration testing can be used to test the functionality of a program prior to the release of the final product.
  • System (End-to-end) testing – These tests represent the top of the pyramid. They are part of the black box testing. The high-level layer is where you write tests that interact with the business logic of your application. These tests usually interact with the app through the UI, just like the end-user would interact. Tests in this test project are run infrequently and are run after you deploy your application to a staging environment or an acceptance testing environment.

A testing pyramid is used to show how much testing a system should get in every level of testing. Only when you combine multiple levels of testing, you can get the most from your testing efforts.

10. Signals when the feature is implemented

Test-driven development is a process that involves the creation of tests for an application before building it. The process is simple: start by writing a test for a feature you need to implement. Then implement the feature. Lastly, refactor the code or your unit test case.

test-driven development (tdd)

Unit tests are a central part of TDD, and by using them to test each component of your application, you ensure that your application is as robust as possible.

They are also the best way to confirm that the code for a particular feature is implemented correctly. But can also serve as a signifier for when a feature is considered “done.”

What do I mean by that?

Well, before you implement your feature, the test is red, it’s failing because the implementation is missing. After you add the code, if the test turns to green, this means that the feature is implemented and you are done.

11. Reduces cost of software development

We live in an era where the cost of software is measured in the millions or even billions. Therefore, it is common practice to test software on a large scale before rolling it out into production. For example, most software projects run some automated test suite before going into production (mirroring the “build-test-measure” process of traditional software development).

While unit testing may not seem like a cheap software testing practice, it actually can save you a lot of time and money, especially when compared to manual testing.

12. Agile process

Unit testing is essential in the agile development process. It allows developers to make changes to the code and verify that the changes do not break any existing functionality.

By running these tests before and after making changes, developers can be confident that their changes have not introduced any new bugs. This increases the quality of the code and reduces the chances of regressions. The developers typically write unit tests, which can be run automatically as part of the build process.


In this post, I have outlined the 12 benefits of unit testing. It enables you to find and fix bugs more efficiently. It also results in happier programmers and better software quality. Good software quality means fewer surprises along the way and more happy customers.

That’s why unit testing should be part of your daily development routine.

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