What is Junit and How it works? An Overview and Its Use Cases

History & Origin of Junit

JUnit was born on a flight from Zurich to Atlanta in 1997 for OOPSLA. Kent Erich was flying with Gamma, and what else were the two geeks doing besides program on a long flight? The first version of JUnit was built there, pair programmed, and tested first (a pleasant form of meta-circular geekery).

What is Junit?

JUnit is a unit testing open-source framework for the Java programming language. Java developers use this framework for writing and executing automated tests. In Java, there are test cases that have to be re-executed every time a new piece of code is added. This is done to ensure that nothing in the code is broken. JUnit has many graphs that represent the progress of a test. When the test runs smoothly, the graph displays a green color, and it turns red when the test fails. JUnit tests enable developers to develop highly reliable and bug-free code.

How Junit works aka Junit architecture?

JUnit 5 architecture and its build blocks. JUnit is one of the most popular unit testing and test runner frameworks. Some teams are still using JUnit 4 but day by day the usage of JUnit 4 is getting less. Thus, it is better to learn and get used to JUnit 5 and its new features.

Use case of Junit?

JUnit is used to do unit testing in Java. A JUnit test case is the set of codes which ensure that our program code works as expected or not. In Java, two types of unit testing are possible, manual testing and automated testing. Manual testing is a special type of testing in which test cases are executed without using any equipment. Unlike manual testing, automated testing is not possible without the support of any equipment. The org.junit package provides several classes and packages, which help us to ensure whether our code provides the expected output or not. These packages and classes are Assert, After, Before and Test, etc.

Feature and Advantage of using Junit?

Advantages of Junit

  • The JUnit framework is open source
  • It provides text-based command lines as well as AWT-based and Swing-based graphical test mechanisms
  • It has some annotations to utilize test functions
  • It has a test runner to test running applications
  • It allows you to write code
  • It can test automatically and provide feedback

Disadvantages of Junit

  • It cannot do dependency testing as opposed to TestNG framework.
  • It’s not suitable for higher level testing i.e. for large test suites.
  • Group testing cannot be done in JUnit, which is available in TestNG.
  • Can’t create HTML reports of test cases. You need to use ANT to create tests HTML reports.

Best Alternative of Junit?

  • JHipster
  • Spring Framework
  • Grails
  • Spark
  • Vaadin
  • Apache OFBiz
  • Hibernate
  • Eclipse AspectJ

Best Resources, Tutorials and Guide for Junit



Free Video Tutorials of Junit

Interview Questions and Answer for Junit

1) What is JUnit?
JUnit is a unit testing framework for the Java application. It allows you to unit test your code at the method level. You can also use JUnit for test-driven development e.g. first writing test and then writing actual code. Most of the Java IDE like Eclipse, Netbeans and IntelliJ Idea provides out-of-box JUnit integration for TDD. Even build tools like Maven, Ant, and Gradle can run the JUnit test at compile and built time.

2) What is Testing?
Testing is the process of checking the functionality of the application whether it fulfills the requirement or not.

3) What is unit testing?
The process of testing individual functionality (known as a unit) of the application is called unit testing.

4) Give some disadvantages of manual testing.
Following are some disadvantages of manual testing:

  • The testing is very time consuming and is very tiring.
  • The testing demands a very big investment in the human resources.
  • The testing is less reliable
  • The testing cannot be programmed.

5) List out some advantages of automated testing.
Some of the advantages of automated testing are:

  • It is very fast.
  • Investment is very less.
  • Testing is more reliable.
  • The testing can be programmed.

6) Is it necessary to write the test case for every logic?
No, we should write the test case only for that logic that can be reasonably broken.

7) What are the useful JUnit extensions?

  • JWebUnit
  • XMLUnit
  • Cactus
  • MockObject

8) What are the features of JUnit?

  • Opensource
  • Annotation support for test cases
  • Assertion support for checking the expected result
  • Test runner support to execute the test case

9) How is the testing of the ‘protected’ method done?
To test the protected method, the test class is declared in the same package as the target class.

10) How is the testing of ‘private’ method done?
There is no direct way for testing of the private method; hence manual testing is to be performed, or the method is changed to “protected” method.

11) If the JUnit method’s return type is ‘string’, what will happen?
JUnit test methods are designed to return ‘void’. So the execution will fail.

12) Is the use of ‘main’ method possible for unit testing?

13) Is it necessary to write the test class to test every class?

14) What does XMLUnit provide?
Junit extension class, XMLTestCase and set of supporting classes is provided by the XMLUnit.

15) List the core components of Cactus.

  • Cactus Framework
  • Cactus Integration Module

16) What are the methods in fixtures?

  • setup
  • tearDown

17) What is the Unit Test Case?
A Unit Test Case is the combination of input data and expected output result. It is defined to test the functionality of a unit.

18) What is the use of @Test annotation?
The @Test annotation is used to mark the method as the test method.

19) What is the test suit?
The test suit allows us to group multiple test cases so that it can be run together. TestSuit is the container class under junit.framework.TestSuite package.

20) What does test runner?
The test runner is used to execute the test cases.

Rajesh Kumar
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