JUnit Interview Questions and Answers

By Umesh Singh
Last update: 30 Mar 2020, 14 Questions
JUnit Interview Questions

Junit is a unit testing framework and is an open source helping in test-driven development. It is used to write and run the Java programs’ test cases. Junit interview questions are one of the topics which take the students’ mind, and they search for the answers to it. There are several factors and the parameters increasing the use of JUnit framework. It also acts as a relationship-builder between development and testing process and is used for testing the application without any use of the server.


  • Increases stability and productivity of the program code
  • Reduces the debugging time
  • Decreases the chances of errors
  • Provides a text-based command line
  • Consists of Swing-based and AWT-based graphical testing for reporting the process

Most Frequently Asked JUnit Interview Questions

1. What is JUnit?

Junit is an important unit Java testing framework and helps in the development of test-driven development. It is a significant part of the family known as xUnit, and hence it got its a name, Junit. Junit framework runs automatically improving the results and providing immediate feedback.

2. What is the use of JUnit?

Junit, an automation framework is used for UI testing and unit testing for the definition of the implementation of the code flown with different Annotations. It assists in writing the codes faster increasing the quality

3. What are the essential features of JUnit?
  • Flexibility- With the help of matches, Junit helps in the assertions of the multiple conditions such as any of(is(“Learn Junit)), constraintstring(“hello)));
  • Enhanced failure messages- In the previous version of JUnit, the coding of the failure message was- org.junit.ComparisonFailure:expected:<hello[] but was :<hello[world]> But in the new version of JUnit, the better is java.lang.AssertionError:Expected: is “hello” but: was &lquo;hello world”
  • Gives annotations for the identification of the test methods.
  • Junit offers test runners for the running tests and assertions for testing expected results.
  • It has simple and less complex taking less time in the operation of the testing process

Junit Interview Questions can be learned easily with us on this online learning platform.

5. What is the purpose of the @AfterClass annotation in JUnit?

In case of the allocation of the expensive external resources in a BeforeClass method, then there is the requirement of releasing them after the running of the tests completes. For this, the annotation of the @AfterClass method, a public static void method is required to be run after all the class’s tests have been run. It is because of the feature of the method such as it guarantees the test is running even in the situation of an exception thrown by BeforeClass. It is one of the methods to be declared in the superclass and run after the running process of the current class ends. Also, it is called once per test class.

6. What are JUnit annotations?

The special form of the syntactic meta-data that can be used for the improved code readability and structure in the source code. The examples of the entities that can be annotated are parameters, methods, variables, classes, and methods in the Java source code. JUnit annotations are Before, After, AfterClass, Ignore, BeforeClass, RunWith, and Test.

7. What is Junit testing?

Junit testing is a framework written in Java for providing a standard way of organizing, writing, and running the tests. An accurate logic of the test can be written following a simple rule. Here, Junit means unit testing which implies the meaning as of checking the individual parts of a software system without the implementation of the entire system from end to end.

8. Why do we use JUnit testing?
The multiple essential features of JUnit testing are the answer to the above question. Some of them are as follows-
  • Useful in providing the status of the result after testing, i.e., shows green on the smooth running of the test, whereas, red is the color in the otherwise case.
  • Test cases can be organized in the form of JUnit tests
  • Helps in the fast writing and execution of the codes
  • Junit testing helps in increasing the quality of the tests
10. Which is better JUnit or TestNG?
S.no TestNG Junit
1. Junit and NUnit inspires this testing framework Are a java library and an instance of xUnit architecture for Unit testing code chunks
2. Easier to use with the help of the new functionalities Some complexities are there
3. An XML file is required to run the suite test @Suite and @RunWith are required to run the suite test
4. Exception testing is available It is available here as well
5. New innovation feature is available in Group test No existence of any Group test here in JUnit
13. Please explain JUnit extensions?
There are four extensions of Junit-
  • XML Unit
  • MockObject
  • Cactus
  • JWebUnit
  • XML Unit- It offers a set of supporting classes, a single JUnit extension class, XMLTestCase allowing the assertions to be made about the validity of a piece of XML, individual nodes in an XML piece which DOM Traversal exposes and many more.
  • MockObject- This extension is used for the simulation of the behavior of the real and complex objects which are useful in the incorporation of the unit test.
  • Cactus- For lowering the cost of writing the tests and the server-side code, the simple test framework is used. It extends the JUnit and executes an in-container strategy which results in the execution of testing inside a container. Cactus Integration Modules and Cactus Framework are the important components of Cactus.
  • JWebUnit- This extension has a simple and unified testing interface wrapping the existing frameworks such as Selenium, and HtmUnit. Navigation of the web applications is done with a set of assertions by this high-level Java API.
14. What is JWebUnit and explain its advantages?

JWebUnit is one of the extensions of JUnit and is a Java-based testing framework for web applications. It offers high-level API of Java used for the navigation of the web applications in addition to the set of assertions for the verification of the authenticity of the application. The main function of JWebUnit is wrapping the existing frameworks for testing with a simple and unified testing interface to check for the credibility of the web applications.

Development History

This open source framework was developed by Erich Gamma and Kent Beck. Look for the best Junit interview questions