The importance of Unit Testing

Software testing is a process to validate and verify that a certain software program or application or product works perfectly as expectation, meeting the business and technical requirements that guided its design and development. During the process, the main purpose of software testing is to find all the bugs that hinder the software from running properly.

There are various testing levels designed to check on bugs and reconnect between the development life-cycle states. SDLC (Software Development Life Cycle) model includes phases such as requirement gathering, analysis, design, coding or execution, testing, and deployment.

All of these phases need to undergo the software testing level process. There are four prominent testing levels:

  1. Unit Testing
  2. Integration Testing
  3. System Testing
  4. Acceptance Testing



Levels of testing
Levels of testing – Copyright from


Unit testing means breaking program/ application into pieces and subject each piece to a series of tests. Developers usually implement these kinds of testing to test each module separately, thus, being able to inspect if component are fulfilling functionalities or not.

Integration testing investigates the combination of how two systems work together. Testers (individual or a test team) check the data flow from one module to other modules. Different modules are combined and tested.

System testing tests general interaction of components, including load, performance, reliability and security testing. System testing is often performed on a complete, integrated system. It is the final test to validate that the system meets all the technical requirements and specifications. It evaluates both functional and non-functional need for testing.

Acceptance testing is implemented to testify if the requirements of a specification or contract are met as per it delivery. Acceptance testing if performed by end user/ customers/ stockholders.

This article will focus on Unit Testing and the reason why many big tech companies embrace Unit Testing. Unit Testing is a part of Agile methodology. To put it simple, a unit test is the smallest software component that is possible to be tested. Since unit is small, test results can be designed, executed, recorded and analyzed almost effortlessly compared to larger chunks of code. The main purpose of unit testing is to isolate and test if individual parts of the program are working correctly. Basically, the smallest part of testable software is singled out from the remainder of the code and then inspected to see if it behaves as expectation. Thanks to this, developers are able to identify bugs much faster, thus, boosting automation testing process.


1. Agile

When it comes to large and complex piece of application, more and more features are added to a software. Changing already tested code at this point can be pricey and tricky. However, with unit test, code refactoring is like “greasing the wheel”. Developers can modify and refactor code much securely and at ease.

2. Improved code quality

Unit testing helps to identify any emerged bug before sending code to integration testing. Writing test before actual coding urges developers to think twice on the problem and more careful at their coding. As a result, better code is produced.

3. Bugs identification at early stage

With unit test, developers are compelled to test their individual code before integration, thus, issues (bugs while implementation and flaws or missing parts of the specification for the unit) can be found at early stage and can be resolved with other piece of codes staying intact and not affected.

4. Simplified integration

As mentioned above, thanks to unit testing, defects are dramatically reduced either in the newly developed feature or when changing the actual functionality. Unit Testing justifies the precision of each unit. After that, the units are integrated into an application and now it is much easier to investigate the whole application during the integration process since individual units have been verified.

5. Helpful documentation

Unit testing provides detailed document of the system. Just by looking at the unit tests, developers will learn at once functionality provided by a unit as well as how to use it.

6. Debugging

By using unit testing, debugging process is unscrambled. In case of test failure, only the latest changes made in the code need to be debugged.

7. Design

Since you have to write the test first, you have to think through in terms of your design and what goals are set for it before you actually write the code. This compels you to create better design because you have to stay focused to assure that the code’s responsibility as well as the code itself has high cohesion.

8. Economical

The sooner the bug is found, the less expense tech companies have to spend on bug fix. If bug is found later on later testing process like system testing or acceptance testing, it will be much more difficult to fix the bug, to identify the source of the bug and the cost will be very excessive.


As the first level of testing in the development life cycle, unit testing plays a crucial role in the creation of a perfectly functional and bug-free application. Most developers will recommend on unit testing as essential and incredibly valuable to projects, especially large projects with larger code base. Unit testing helps to significantly reduce the amount of bugs during deployment, hence, this testing level can never be skipped even when the budget and deadline are tight.

At Bac Ha Software Co.,Ltd. all testing levels are utilized and fulfilled. We make sure all steps that lead to the perfect creation of final product are implemented properly. Our process is highly professional keeping in mind that customer satisfaction is our ultimate goal.