Guide to Unit Testing

Unit testing

If you are new in the software world, then the word Unit Testing will bring back your school memories. But, if you are from a software background, you may encounter the word Unit Testing daily. Yes, the term is that common and that important for the quality of the code. So let us know what Unit Testing is!

Table of Contents

What is unit testing?

Unit testing is one of the initial methods/tests used for software testing. It tests the individual units of the source code. The unit test identifies if there is any problem in the source code about individual units. It crosschecks whether the individual Unit is correct and functioning or not. 

For example, you have written a code, and you want to test if a statement is working or not. So, you run a test and see if the statement is functioning. Now that is unit testing. This is a manual type of testing. But there are different frameworks available to automate unit testing for different programming languages.

If you are thinking, who handles the unit testing? Then the answer is pretty simple. The developer’s total responsibility is to do unit tests on the program in the initial stages.

What is the Unit in Unit Testing?

A Unit in the unit testing is the smallest element of the code that one can execute individually. 

What are the types of unit testing?

A unit test is of three types. Each type of unit test has its function and purpose in testing. So let us know about them.

  1. White-Box Testing

    – Generally, the software developers do White-Box testing. The white-box testing tests the internal parts of the code, which is beyond the user interface. In this test, the tester exercises some inputs to determine the suitable outputs.
  1. Black-Box Testing

    – Black box testing is a test done by the software tester. It does the test on the functionality of the application or the software. It tests the user interface of the application/software. It does not need any knowledge of the internal structure of the code.
  1. Grey-Box Testing

    – Grey box testing finds any improperness in the application. It is a combination of both white box and black-box testing. 

What is the Importance of unit testing?

Unit tests ensure the quality of the code. Unit test checks that if any mistakes in the code may harm the final product. So, it is quite difficult to find mistakes in the source code in the initial stages without unit testing. 

Unit tests are elementary to run and take very little time. Hence, unit tests are time-saving and useful for the quality of the code.

Moreover, unit tests are significant because unit tests identify the bugs or any mistake in the code. It identifies the bugs in the initial stages of the development of the program. If it does not identify the bugs in the initial stages, it can cause many issues later. It can cause too much waste of money, time, and other resources in later processes.

How to run unit tests automatically? 

Unit tests run both manually and automatically. Manual unit tests are also necessary. But running unit tests automatically is more reliable, gives accurate results, and makes life easy. There are several frameworks used for this purpose for different programming languages. For example, NUnit, JUnit, TestNG, Embunit, HtmlUnit, Cucumber, and XCTest are unit test frameworks. 

Now you may ask what do you mean by the framework for unit testing. To state, frameworks are just software tools using which you can run unit tests automatically. All the frameworks are readily available on the web.

To understand correctly, let us take an example with a popular unit-testing framework, which is JUnit. JUnit is a trendy unit test framework that one can use for the Java programming language.

Junit also supports automation testing. To use automated testing, all you have to do is use annotations like @Before, @After,@Test, @Beforeclass, @Afterclass. Using this annotation, you can perform unit tests automatically several times. Here is the link to know more about these annotations.

How do I start unit testing?

 Is that your question? Then your solution is relatively easy. So let us assume you are in the initial phase of developing a program. You are writing some codes and want to check if you are doing everything right! It is time you use unit tests. 

Thus, you have written some conditions and statements in the code. Now write a test condition for them and check if the code works appropriately or not. Repeat for all the codes you have written. If this seems laborious, then you can always use automated unit test frameworks.

What is unit test coverage? How do you measure it?

Unit test coverage is the percentage of lines covered under unit test cases to the source code’s total number of lines. You can measure it with the simple formula, which is [(number of lines executed by unit test cases/ number of lines in the source code) * (100)]. Otherwise, you can use Test coverage tools like JaCoCo,, EMMA, Cobertura, etc.

Now you may be thinking about how much unit test coverage would be appropriate for the program. It depends on your unit test plan. For some, 60% is OK, and some need 80% or 100%. 

What is the difference between unit testing and integration testing?

Many people mix up both the terms when it comes to unit testing and integration testing. Let me clarify to you in unit testing tests that individual units and integration testing combine and test a group of modules.

Besides, it is necessary to remember that the developer performs unit tests, and the testing teams do the integration tests.

Now you may ask, which one is essential unit testing or integration testing? Well, both of the tests are equally important to maintain the quality of the code. Unit tests run in the initial stages of the development of the program. Integration tests run after unit testing and before the system testing.

Compared to integration tests, unit tests are relatively easy to perform and give more accurate results. Integration testing is black-box testing. Whereas unit testing is, classify under white box testing 

What is the difference between Unit testing and Regression Testing?

When individual units in the source code are tested, it is unit testing. Besides, when already executed codes are re-executed, then it is regression testing. Regression testing ensures the quality of the code.

If new codes add-up to the program, it is necessary to check if the program is running fine or not. It is the reason to recommend regression testing… If there is any change in the existing source code, then regression testing is necessary.

Now let us look into some other questions people commonly have about unit testing!

Who does the Unit Tests?

Well, a tester or a developer, any can do unit tests. But, it is the developer’s responsibility to do the unit testing in the initial stages of the development.

What is a Unit Testing Framework?

Unit Testing Frameworks are software tools that one can use for Unit Testing. There are different frameworks available on the web for different programming languages. Most of these frameworks support automatic unit testing. They provide more accurate and faster unit test results 

What are the different Unit Testing Frameworks?

There are many Unit Testing frameworks available. The best of them are 

  • TestNG
  • JUnit
  • NUnit
  • HtmlUnit
  • Typemock
  • Unity Test Tools
  • Cantana 
  • Parasoft
  • EMMA
  • EmbUnit
  • SimpleTest
  • Microsoft Unit Testing Framework
  • Jasmine
  • JMockit
  • XCTest

These are some of the most used unit testing frameworks. TestNG, Junit, and NUnit are frameworks for unit testing in Java.

Is XCTest a Unit Testing Framework?

Yes, XCTest is a unit testing framework. IOS uses this framework for Xcode programs. 

Code Coverage & RKTracer:

Unit Tests are essential for development. Unfortunately, unit tests do not cover each line of the source code. The percentage of lines covered by unit testing is the code coverage percentage. 

Every developer wants good code coverage results. It is difficult for a human to calculate the lines the unit test is covering and which it is not. So we use code coverage tools to know the actual code coverage percentage. These tools will help the developer to know how to improve his unit tests.  

RKTracer is the best tool for code coverage available right now. It supports essential programming languages like Python, Golang, Kotlin, and Swift. It is compatible with most operating systems like Linux, Microsoft Office, Apple Mac OS, and Android. 

RKTracer supports all coverage levels of code coverage. It supports all Line Coverage, Statement Coverage, Branch Coverage, Condition Coverage, and Multiple Condition Coverage. RKTracer has a very user-friendly interface and generates an HTML and XML report of the testing.


So, we understood that the Unit Test tests the individual units from the source code. It is an essential and widespread aspect when it comes to software development. Unit testing is so easy that a beginner can learn in very little time. It is so important that even an expert software developer have to use unit testing to maintain the code’s quality. If you are a beginner, now we how important it is to do unit tests. The unit test will improve the quality of both the source code and the developer.


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