Top 11 JUnit interview questions

1) Explain what is JUnit?

JUnit is a testing framework for unit testing. It uses Java as a programming platform, and it is

an Open Source Software managed by the JUnit.org community.

2) Explain what is Unit Test Case?

Unit Test Case is a part of the code that ensures that the another part of code (method)

behaves as expected. For each requirement, there must be at least two test cases one negative

test and one positive test.

3) Explain how you can write a simple JUnit test case?

Determine a subclass of TestCase

To initialize object(s) under test, override the setup() method

To release object(s) under test override the teardown() method

Determine one or more public test XYZ() methods that exercise the objects under test and

assert expected results.

4) Mention what are parameterized tests?

Parameterized tests enable developer to perform the same test over and again using different

values.

5) Mention what is the difference between JUnit and TestNG?

JUnit TestNG

In JUnit the naming convention for

annotation is a bit complicated for,

e.g., “Before”, “After” and

“Expected”

In JUnit, for a method declaration

you have to follow a specific style

like using “@BeforeClass” and

In TestNG it is easier to understand

annotations like “BeforMethod”,

“AfterMethod” and

“ExpectedException”

In TestNG, there is no restriction

like you have to declare methods in

a specific format

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“@AfterClass”.

In JUnit method name constraint is

present

JUnit framework does not have

“Parameterized Test” or

“Dependency Test” feature

In JUnit grouping of test cases are

not available

JUnit does not support parallel

execution on Selenium test cases

It cannot re-run the failed cases

In TestNG method name constraint

is not present, and you can

determine any test method names

TestNG use “dependOnMethods”

to implement the dependency

testing

In TestNG, grouping of test cases is

available

In TestNG Parallel execution of

Selenium test cases are possible

It can rerun the failed tests

6) Mention different methods of exception handling in JUnit?

There are different methods of exception handling in JUnit

Try catch idiom

With JUnit rule

With @Test annotation

With catch exception library

With customs annotation

7) Explain what is ignore test in JUnit?

When your code is not ready, and it would fail if executed then you can use @Ignore

annotation.

It will not execute a test method annotated with @Ignore

It will not execute any of the test methods of test class if it is annotated with @Ignore

8) List out some useful JUnit extensions?

JUnit extensions include

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Cactus

JWebUnit

XMLUnit

MockObject

9) Explain who should use JUnit - a developer or tester? Why you use JUnit to test your

code?

JUnit is more often used by developers to implement unit tests in JAVA. It is designed for unit

testing that is more a coding process and not a testing process. However, many testers and QA

engineers use JUnit for unit testing.

JUnit is used because

It test early and does automate testing

JUnit tests can be compiled with the build so that at unit level, regression testing can be

done

It allows test code re-usage

JUnit tests behave as a document for the unit tests when there is a transfer

10) Explain what is JUnitCore Class?

JUnitCore class is an inbuilt class in JUnit package; it is based on Façade design pattern, this

class is used to run only definite test classes only.

11) Explain how you can run JUnit from the command window?

To run JUnit from the command window, you have to follow the steps

Set the CLASSPATH

Invoke the runner:

Java org.junit.runner.JUnitCore