Interview Questions.

Top 100+ Junit Interview Questions And Answers

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Top 100+ Junit Interview Questions And Answers

Question 1. What Is Testing?

Answer :

Testing is the procedure of checking the capability of the application whether or not it is running as per requirements.

Question 2. What Is Unit Testing?

Answer :

Unit trying out is the testing of single entity (elegance or technique). Unit checking out is very critical to every software program organisation to offer a first-class product to their customers.

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Question three. What Is Manual Testing?

Answer :

Executing the test instances manually without any tool help is known as guide testing.

Question four. What Is Automated Testing?

Answer :

Taking device guide and executing the test instances by using automation device is called automation testing.

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Question five. What Are The Disadvantages Of Manual Testing?

Answer :

Following are the disadvantages of manual checking out −

Time consuming and tedious − Since test cases are completed by using human assets so it is very slow and tedious.
Huge funding in human resources − As test cases want to be executed manually so more testers are required in manual testing.
Less reliable − Manual checking out is less dependable as assessments won't be carried out with precision every time because of human mistakes.
Non-programmable − No programming can be finished to write sophisticated exams which fetch hidden information.
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Question 6. What Are The Advantages Of Automated Testing?

Answer :

Following are the benefits of computerized testing −

Fast − Automation runs check instances drastically faster than human assets.
Less funding in human resources − Test cases are accomplished by the usage of automation tool so less tester are required in automation trying out.
More reliable − Automation exams perform precisely equal operation whenever they may be run.
Programmable − Testers can application state-of-the-art tests to carry out hidden information.
Question 7. What Is Junit?

Answer :

JUnit is a Regression Testing Framework used by builders to put in force unit testing in Java and accelerate programming velocity and boom the first-rate of code.

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Question eight. What Are Important Features Of Junit?

Answer :

Following are the crucial functions of JUnit −

It is an open source framework.
Provides Annotation to discover the test techniques.
Provides Assertions for trying out expected outcomes.
Provides Test runners for running checks.
JUnit checks can be run routinely and that they take a look at their own effects and provide instant feedback.
JUnit assessments may be organized into test suites containing check instances or even other check suites.
JUnit shows check progress in a bar this is inexperienced if take a look at is going pleasant and it turns pink when a take a look at fails.
Question nine. What Is A Unit Test Case?

Answer :

A Unit Test Case is part of code which ensures that the some other a part of code (approach) works as predicted. To attain the ones favored consequences quick, check framework is needed .JUnit is best unit take a look at framework for java programming language.

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Question 10. What Are The Best Practices To Write A Unit Test Case?

Answer :

A formal written unit test case is characterized by using a known input and through an anticipated output, which is worked out before the test is finished. The known input should check a precondition and the predicted output must test a postcondition.

There ought to be as a minimum  unit take a look at cases for every requirement: one positive take a look at and one negative test. If a requirement has sub-requirements, every sub-requirement need to have at least two take a look at cases as positive and negative.

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Question eleven. When Are Unit Tests Written In Development Cycle?

Answer :

Tests are written earlier than the code at some stage in improvement so as to assist coders write the excellent code.

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Question 12. Why Not Just Use System.Out.Println() For Testing?

Answer :

Debugging the code using gadget.Out.Println() will cause manual scanning of the complete output on every occasion this system is administered to ensure the code is doing the predicted operations. Moreover, ultimately, it takes lesser time to code JUnit techniques and test them on magnificence documents.

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Question thirteen. How To Install Junit?

Answer :

Follow the steps under −

Download the contemporary model of JUnit, stated beneath as junit.Zip.
Unzip the junit.Zip distribution document to a listing called %JUNIT_HOME%.
Add JUnit to the classpath −
set CLASSPATH=%CLASSPATH%;%JUNIT_HOMEpercentjunit.Jar
Test the installation via running the sample checks allotted with JUnit (pattern assessments are placed in the installation directory directly, now not the junit.Jar document). Then absolutely type −
java org.Junit.Runner.JUnitCore org.Junit.Exams.AllTests
All the tests need to pass with an "OK" message. If the exams do not skip, confirm that junit.Jar is inside the CLASSPATH.
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Question 14. Why Does Junit Only Report The First Failure In A Single Test?

Answer :

Reporting a couple of failures in a single test is generally a signal that the test does an excessive amount of and it's miles too big a unit take a look at. JUnit is designed to paintings high-quality with some of small assessments. It executes every check within a separate instance of the test elegance. It reports failure on each take a look at.

Question 15. In Java, Assert Is A Keyword. Won't This Conflict With Junit's Assert() Method?

Answer :

JUnit 3.7 deprecated assert() and changed it with assertTrue(), which fits exactly the identical way. JUnit four is like minded with the assert key-word. If you run with the -ea JVM transfer, assertions that fail can be said by JUnit.

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Question sixteen. How Do I Test Things That Must Be Run In A J2ee Container (e.G. Servlets, Ejbs)?

Answer :

Refactoring J2EE components to delegate capability to different items that do not should be run in a J2EE box will improve the design and testability of the software program. Cactus is an open supply JUnit extension that may be used for unit testing server-aspect java code.

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Question 17. Name The Tools With Which Junit Can Be Easily Integrated?

Answer :

JUnit Framework may be easily integrated with either of the followings −

Eclipse
Ant
Maven
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Question 18. What Are The Core Features Of Junit?

Answer :

JUnit take a look at framework presents following essential capabilities −

Fixtures
Test suites
Test runners
JUnit lessons
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Question 19. What Is A Fixture?

Answer :

Fixture is a fixed nation of a hard and fast of items used as a baseline for strolling exams. The cause of a test fixture is to ensure that there may be a widely recognized and glued environment wherein assessments are run so that consequences are repeatable. It consists of following methods −

setUp() method which runs earlier than each take a look at invocation.
TearDown() approach which runs after each test method.
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Question 20. What Is A Test Suite?

Answer :

Test suite way package deal a few unit take a look at instances and run it collectively. In JUnit, each @RunWith and @Suite annotation are used to run the suite check.

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Question 21. What Is A Test Runner?

Answer :

Test runner is used for executing the test cases.

Question 22. What Are Junit Classes? List Some Of Them?

Answer :

JUnit instructions are important classes which are utilized in writing and checking out JUnits. Some of the crucial lessons are −

Assert − It consists of a set of assert methods.
TestCase − It carries a take a look at case defines the fixture to run more than one exams.
TestResult − It incorporates techniques to accumulate the consequences of executing a take a look at case.
TestSuite − It is a Composite of Tests.
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Question 23. What Are Annotations And How Are They Useful In Junit?

Answer :

Annotations are like meta-tags that you can add to you code and follow them to techniques or in elegance. The annotation in JUnit offers us facts approximately check techniques, which methods are going to run before & after check techniques, which strategies run earlier than & after all the techniques, which methods or elegance might be forget about throughout execution.

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Question 24. How Will You Run Junit From Command Window?

Answer :

Follow the steps under −

Set the CLASSPATH
Invoke the runner −java org.Junit.Runner.JUnitCore 
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Question 25. What Is The Purpose Of Org.Junit.Assert Class?

Answer :

This class affords a set of declaration strategies useful for writing checks. Only failed assertions are recorded.

Question 26. What Is The Purpose Of Org.Junit.Testresult Class?

Answer :

A TestResult collects the results of executing a test case. It is an instance of the Collecting Parameter pattern. The test framework distinguishes between screw ups and mistakes. A failure is predicted and checked for with assertions. Errors are unanticipated problems like an ArrayIndexOutOfBoundsException.

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Question 27. What Is The Purpose Of Org.Junit.Testsuite Class?

Answer :

A TestSuite is a Composite of Tests. It runs a collection of test cases.

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Question 28. What Is The Purpose Of @check Annotation In Junit?

Answer :

The Test annotation tells JUnit that the public void technique to which it's miles attached may be run as a check case.

Question 29. What Is The Purpose Of @before Annotation In Junit?

Answer :

Several checks need comparable gadgets created earlier than they could run. Annotating a public void approach with @Before reasons that technique to be run before every Test method.

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Question 30. What Is The Purpose Of @after Annotation In Junit?

Answer :

If you allocate external assets in a Before technique you need to launch them after the take a look at runs. Annotating a public void approach with @After causes that technique to be run after the Test approach.

Question 31. What Is The Purpose Of @beforeclass Annotation In Junit?

Answer :

Annotating a public static void approach with @BeforeClass reasons it to be run once earlier than any of the take a look at methods within the class.

Question 32. What Is The Purpose Of @afterclass Annotation In Junit?

Answer :

This will perform the method after all exams have finished. This can be used to carry out smooth-up sports.

Question 33. What Is @ignore Annotation And How Is This Useful?

Answer :

Following are a number of the usefulness of @Ignore annotation −

You can without problems discover all @Ignore annotations in the source code, even as unannotated or commented out assessments aren't so easy to locate.

There are instances whilst you cannot fix a code this is failing, but you still need to approach to be round, precisely so that it does now not get forgotten. In such instances @Ignore makes feel.

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Question 34. Explain The Execution Procedure Of The Juint Test Api Methods?

Answer :

Following is how the JUnit execution process works −

First of all technique annotated as @BeforeClass execute simplest once.
Lastly, the technique annotated as @AfterClass executes simplest as soon as.
Method annotated as @Before executes for each check case but earlier than executing the test case.
Method annotated as @After executes for every take a look at case however after the execution of check case.
In between method annotated as @Before and method annotated as @After each take a look at case executes.
Question 35. What Is The Purpose Of Org.Junit.Junitcore Class?

Answer :

The check instances are achieved the use of JUnitCore magnificence. JUnitCore is a facade for running assessments. It supports jogging JUnit four assessments, JUnit 3.8.X assessments, and combinations.

Question 36. How To Simulate Timeout Situation In Junit?

Answer :

Junit gives a reachable option of Timeout. If a take a look at case takes greater time than exact range of milliseconds then Junit will routinely mark it as failed. The timeout parameter is used along side @Test annotation.

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Question 37. How Can You Use Junit To Test That The Code Throws Desired Exception?

Answer :

JUnit provides a alternative of tracing the Exception handling of code. You can check if a code throws preferred exception or no longer. The predicted parameter is used along side @Test annotation as follows − @Test(predicted)

Question 38. What Are Parameterized Tests?

Answer :

Junit four has added a brand new feature Parameterized exams. Parameterized checks allow developer to run the equal check again and again once more the usage of exclusive values.

Question 39. How To Create Parameterized Tests?

Answer :

There are five steps, which you need to comply with to create Parameterized checks−

Annotate take a look at class with @RunWith(Parameterized.Elegance).
Create a public static approach annotated with @Parameters that returns a Collection of Objects (as Array) as test records set.
Create a public constructor that takes in what is equal to 1 "row" of test facts.
Create an instance variable for each "column" of take a look at information.
Create your tests case(s) the usage of the instance variables as the source of the take a look at statistics.
The check case can be invoked as soon as according to every row of records. Let's see Parameterized checks in movement.
Question forty. How Do You Use Test Fixtures?

Answer :

Fixtures is a hard and fast kingdom of a fixed of gadgets used as a baseline for jogging assessments. The purpose of a take a look at fixture is to make certain that there is a widely recognized and fixed surroundings wherein tests are run in order that results are repeatable. It includes −

setUp() method which runs earlier than every take a look at invocation.
TearDown() approach which runs after each test method.
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Question 41. How To Compile A Junit Test Class?

Answer :

Compiling a JUnit check magnificence is like compiling another Java training. The most effective factor you need be careful is that the JUnit JAR file ought to be protected in the classpath.

Question forty two. What Happens If A Junit Test Method Is Declared As "private"?

Answer :

If a JUnit check method is asserted as "non-public", it compiles successfully. But the execution will fail. This is due to the fact JUnit requires that all take a look at techniques must be declared as "public".

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Question forty three. How Do You Test A "included" Method?

Answer :

When a way is asserted as "covered", it may best be accessed within the identical package deal in which the elegance is described. Hence to test a "covered" approach of a goal class, outline your test magnificence in the equal package deal because the goal magnificence.

Question forty four. How Do You Test A "personal" Method?

Answer :

When a way is said as "non-public", it may handiest be accessed inside the equal elegance. So there may be no way to check a "personal" method of a goal magnificence from any test class. Hence you want to carry out unit testing manually. Or you need to exchange your approach from "personal" to "blanketed".

Question forty five. What Happens If A Junit Test Method Is Declared To Return "string"?

Answer :

If a JUnit test technique is said to go back "String", the compilation will pass good enough. But the execution will fail. This is due to the fact JUnit calls for that all take a look at techniques need to be declared to return "void".

Question forty six. Can You Use A Main() Method For Unit Testing?

Answer :

Yes you can take a look at using predominant() technique. One obvious benefit appears to be that you could whitebox check the magnificence. That is, you can check the internals of it (personal methods for instance). You can not do that with unit-assessments. But basically the take a look at framework tests the interface and the conduct from the consumer's perspective.

Question forty seven. Do You Need To Write A Test Class For Every Class That Needs To Be Tested?

Answer :

No. We want no longer write an impartial test class for every class that needs to be examined. If there is a small institution of tests sharing a commonplace test fixture, you could pass those checks to a brand new test elegance.

Question forty eight. When Are Tests Garbage Collected?

Answer :

The test runner holds robust references to all Test times for the duration of the test execution. This way that for a very long test run with many Test times, not one of the checks may be garbage collected till the quit of the complete take a look at run. Explicitly putting an item to null within the tearDown() approach, for instance, permits it to be garbage gathered before the end of the complete test run.

Question 49. What Is A Mock Object?

Answer :

In a unit check, mock gadgets can simulate the conduct of complex, real (non-mock) items and are therefore useful while a real object is impractical or not possible to comprise right into a unit check.

Question 50. Explain Unit Testing Using Mock Objects?

Answer :

The commonplace coding fashion for checking out with mock objects is to −

Create instances of mock gadgets.
Set country and expectations in the mock gadgets.
Invoke area code with mock items as parameters.
Verify consistency within the mock items.
Question fifty one. Name Some Of The Junit Extensions?

Answer :

Following are the JUnit extensions −

Cactus
JWebUnit
XMLUnit
MockObject
Question fifty two. What Is Cactus?

Answer :

Cactus is a easy test framework for unit testing server-side java code (Servlets, EJBs, Tag Libs, Filters). The intent of Cactus is to decrease the cost of writing exams for server-side code. It uses JUnit and extends it. Cactus implements an in-container approach, meaning that exams are done inside the container.

Question fifty three. What Are The Core Components Of Cactus?

Answer :

Cactus Ecosystem is fabricated from numerous additives −

Cactus Framework is the coronary heart of Cactus. It is the engine that provides the API to put in writing Cactus exams.
Cactus Integration Modules are front ends and frameworks that provide easy approaches of using the Cactus Framework (Ant scripts, Eclipse plugin, Maven plugin).
Question fifty four. What Is Jwebunit?

Answer :

WebUnit is a Java-based trying out framework for web packages. It wraps current checking out frameworks which includes HtmlUnit and Selenium with a unified, easy trying out interface to let you fast take a look at the correctness of your internet packages.

Question 55. What Are The Advantages Of Using Jwebunit?

Answer :

JWebUnit gives a high-stage Java API for navigating a web software combined with a set of assertions to confirm the application's correctness. This consists of navigation through hyperlinks, shape access and submission, validation of table contents, and other common business web application functions.

The simple navigation strategies and geared up-to-use assertions permit for greater rapid check introduction than the use of handiest JUnit or HtmlUnit. And if you need to switch from HtmlUnit to other plugins including Selenium (to be had soon), there's no want to rewrite your checks.

Question fifty six. What Is Xmlunit?

Answer :

XMLUnit affords a single JUnit extension magnificence, XMLTestCase, and a fixed of assisting training.

Question 57. What Is The Use Of Supporting Classes In Xmlunit?

Answer :

Supporting instructions permit assertions to be made approximately−

The differences among two pieces of XML (via Diff and DetailedDiff instructions).
The validity of a piece of XML (through Validator elegance).
The outcome of remodeling a piece of XML the use of XSLT (thru Transform magnificence).
The assessment of an XPath expression on a piece of XML (via instructions enforcing the XpathEngine interface).
Individual nodes in a piece of XML which might be uncovered by means of DOM Traversal (via NodeTest class).




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