What Is Unit Testing? Definition, Basics, and Types

“Hey, man! Is there anything wrong with the new app? It keeps crashing! Planning to use a different one.” Think if you are the owner of that app and you keep on losing users. Your business will disappear in no time.

Well, the scary part is that it can be a common scenario in today's competitive market. The number of users and their demands for efficient tech products with advanced features seem to have no intention to stop.

And, to utilize that business opportunity, numerous small to big companies are jumping in to build awesome applications.

However, despite putting great effort into developing so many products, many businesses are crashing due to a small mistake.

Yes, we are talking about software testing, or better to say testing as a whole. In a product's journey, the testing part is the same or sometimes even more important than developing numerous functionalities.

You may build an app with a lot of useful features but it will never do any good if you do not prioritize testing the functionalities in-depth for improving their quality and use unit testing tools.

That's why Quality Assurance (the defining term of software testing) is a truly crucial part of an application's life cycle.

Here, we are going to dive a little deeper into software testing by discussing a very important part of it i.e. Unit Testing.

It will fill you with an in-depth understanding of the strongest foundation of the huge structure named Software Testing about which you must get the complete idea from the article “STLC (Software Testing Life Cycle) - A Detailed Walkthrough”.

What Is Unit Testing?

As the name suggests, unit testing is concerned with units/the smallest isolated parts of an application. That means the process of testing the small parts of a software application without depending on any external system is called Unit Testing.

Any component that interacts with any external database, files, or deals with the network, cannot be tested as part of the unit testing. For testing the isolated components, the unit tests are mainly conducted during the early development phase of the product.

Though these tests are mostly executed by developers or QA engineers, the amazing codeless testing tools like Preflight enable anyone to execute every type of test regardless of having coding knowledge.

Even from the testing pyramid, the strategy followed for testing purposes, you can clearly see that Unit Testing is executed during the early stages of the entire test suite.

As you move ahead with going through this article, you will get to know everything about it.

How Does Unit Testing Work?

You have already got an idea about the immense importance of unit testing. It is the largest subset of the entire test suite.

So, naturally, it will include a long step-by-step process for successful execution. Generally, the unit tests are completed through 3 steps that are as follows-

  • Planning.
  • Deciding the test cases and preparing the scripts.
  • Executing the unit tests.

Efficient unit tests are part of test-driven development (TDD), a practical methodology with an attention to detail with the objective of building a great product through continuous testing and revision. Due to TDD, developers follow a useful practice of writing the failing unit tests first.

The next steps are writing code and refactoring the application until the tests show successful results. However, Preflight provides a truly codeless testing experience without any hassle.

As you already saw, one of the topmost priorities in unit testing is that the test cases should not depend on each other. To ensure that, each test case is executed independently in an isolated environment.

Also, for the best results, the following points must be followed during the unit tests -

  • Criteria to verify each test case must be included in the code.
  • To report failed tests, a unit test framework should be used.
  • It is not a good practice to create a test for every line of code as it may end up taking too much time.
  • The tests must focus on dealing with only the codes that the users will directly interact with.

You can clearly see above that unit tests are mainly concerned with the points that directly affect the performance of the unit being tested. This allows developers to stay without the worry that how those test cases will affect the functioning of other units or the entire application.

After the successful execution of all the unit test cases, once it is observed that the all the units are performing at their best and being error-free, the larger components are tested by Integration testing which you can get to know a lot about in the article “Testing Pyramid - A Path To Achieve Efficient QA”.

Unit tests are the most frequent form of testing and though they can be done manually, the best practice is to automate them using an efficient unit testing tool like Preflight.

Types of Unit Testing

As you can see in the “Testing Pyramid” article, Unit Testing is the largest subset of the test suite. So, naturally, it is expected to have a wide range of types. But, for simplicity, Unit Testing is mainly categorized into two types i.e. Manual and Automated. Let's take a look at those types for a better understanding.

Manual Unit Testing

You already know that unit tests can be executed both manually and through automation. Though the manual testing approach was conventionally used during the initial period of techincal evolution, the amazing benefits of automated testing surpassed it easily and became the most popular choice for everyone. In manual unit testing, documents with the typical methodologies are followed for the best results.

Hence, you can consider the manual testing approach as a much more static one.

Automated Unit Testing

We are living in the era of automation. The world is working tirelessly to improve efficiency in every field by implementing automation there. Similarly, using test automation tools can also significantly boost the overall efficiency in Unit tests. And, the advantages of test automation do not stop here.

Automating your tests with the amazing no-code test automation tool Preflight can let all your team members work collaboratively regardless of having coding knowledge of the automated tests.

With this tool, you just have to go through your application once and use the functionalities that you wish to test, and your tests will be created and auto-recorded. Then, you can run them as many times as you want and analyze the results deeply.

Also, with more efficiency than the popular unit testing frameworks like Selenium, Preflight enables you to easily set visual and text assertions for the crucial points in the UI that the users will interact with.

To experience all such advantages along with other benefits like reporting the failed test cases and providing a summary of the test cases, you just need to start with booking a demo.

Advantages and Disadvantages of Unit Testing

Every innovation of technology has both advantages and disadvantages.

Similarly, where Unit Testing is a blessing based on numerous aspects, you may also feel like it has some drawbacks too. So, let's discuss those advantages and disadvantages in detail.


  • As these tests are executed during the early stages of the development phase, the problems are identified sooner. Due to this, the number of massive errors decreases.
  • Unit tests enable you to fix the problems earlier and exempt you from the high cost of fixing them later.
  • Lets you enjoy easy debugging processes.
  • The test codes are reusable so, developers get the advantage of using them in other projects.
  • Unit tests make it easy to quickly modify the codebase.


  • Unit tests cannot identify every bug.
  • These tests only deal with sets of data and their functionalities. They are unable to identify errors in integration.
  • In some cases, testing a single line of code requires several lines of code. This eventually leads to a wastage of time and resources.
  • These may make you learn a lot of things using automated testing tools. But, while using Preflight, all you have to do is navigate through your app and that makes it one of the most effective no-code test automation tools.


From this article, you got a good idea about how important is to perform unit testing. It is the foundation/the strongest part of the entire test suite of your app.

Whereas traditional testing tools can make it cumbersome for you to execute these time-consuming tests, the amazing and popular unit testing tools such as no-code testing Preflight allow you to achieve an unimaginable efficiency. This article carries a good amount of description about these crucial tests.

However, soon we'll be coming up with another awesome article on “An Introductory Guide To Unit Testing”. For that, keep an eye on our blog page. And, to experience the new era of testing, click here.