JUnit - Interview Questions and Answers for 'Junit' | Search Interview Question

JUnit - Interview Questions and Answers for 'Junit' - 28 question(s) found - Order By Newest

Q1. What is JUnitRunner ?

Ans. A JUnit Runner is a class that extends JUnit’s abstract Runner class and it is responsible for running JUnit tests.

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Q2. Which of the following is not the advantage of Mocking frameworks ?

a. It helps testing the module independently
b. It helps in faster unit testing
c. It helps in testing code even when external dependencies like service calls are not working
d. It helps in doing end to end Integration Testing

Ans. It helps in doing end to end Integration Testing

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Q3. How to create a Junit to make sure that the tested method throws an exception ?

Ans. Using annotation Test with the argument as expected exception.

@Test (expected = Exception.class)

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Q4. How should we ignore or avoid executing set of tests ?

Ans. We can remove @Test from the respective test so as to avoid its execution. Alternatively we can put @Ignore annotation on the Junit file if we want to ignore all tests in a particular file.

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Q5. How can we test methods individually which are not visible or declared private ?

Ans. We can either increase their visibility and mark them with annotation @VisibleForTesting or can use reflection to individually test those methods.

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Q6. What are the steps to be performed while coding Junit with Mocking framework ?

JUnit

Ans. Initialize required objects for working with mocks and tested method
Set the mock behaviour on dependent objects
Execute the tested method
Perform assertions
Verify if a method is invoked or not

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Q7. What is assert keyword used for ?

Ans. The assert keyword is used to make an assertionâ€”a statement which the programmer believes is always true at that point in the program. This keyword is intended to aid in testing and debugging.

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Q8. Difference between Assert and Verify ?

Testing

Ans. Assert works only if assertions ( -ea ) are enabled which is not required for Verify.Assert throws an exception and hence doesn't continue with the test if assert evaluates to false whereas it's not so with Verify.

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Q9. What are the annotations used in Junit with Junit4 ?

Ans. @Test

The Test annotation indicates that the public void method to which it is attached can be run as a test case.

@Before

The Before annotation indicates that this method must be executed before each test in the class, so as to execute some preconditions necessary for the test.

@BeforeClass

The BeforeClass annotation indicates that the static method to which is attached must be executed once and before all tests in the class.

@After

The After annotation indicates that this method gets executed after execution of each test.

@AfterClass

The AfterClass annotation can be used when a method needs to be executed after executing all the tests in a JUnit Test Case class so as to clean-up the set-up.

@Ignores

The Ignore annotation can be used when you want temporarily disable the execution of a specific test.

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Q10. What should I do if I want to make sure that a particular method of a class is getting called ?

Ans. If its a static method of the class , we can use verify to make sure its getting called.

If its an instance method , We can mock the object and then use verify with the mocked object to make sure that the method is getting called.

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Q11. What is the use of Mockito.any ?

Ans. In case we need to verify that a method is being called with any argument and not a specific argument we can use Mockito.any(Class), Mockito.anyString, Mockito.anyLong etc.

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Q12. Name few Java Mocking frameworks ?

Ans. Mockito, PowerMock, EasyMock, JMock, JMockit

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Q13. Which of the following annotation is used to avoid executing Junits ?

a. @explicit
b. @ignore
c. @avoid
d. @NoTest

Ans. @ignore

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Q14. Write a Test Case using Mock ?

Testing

Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?keyword=mock&category=code

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Q15. What is the use of @Before annotation ?

Junit

Ans. When executing tests it is common that multiple tests need similar objects to be created before they can run. @before specifies a method that provide that initialization for the set of Unit Tests.

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Q16. Have you ever tried mocking static methods ?

Testing

Ans. Yes, that can be done using Power Mock. Mockito doesnt provide a way to mock static methods.

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Q17. Does a Junit without any assertions makes any sense ?

Junit

Ans. Yes, If we are testing a code segment to check if throws / doesn't throw an exception. Moreover while testing void methods, we may just verify and not use assert.

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Q18. What are the benefits of assertThat over assert in Junits ?

Junit

Ans. assertThat is introduced with Junit4 and offers many advatanges over assert. Messages are more explanatory, offer better type safety and are more readable. Moreover hamcrest library is portable as it can used both with junit and TestNG.Moreover assertThat provides flexibility as the same method can be used for assert , assertEquals,assertTrue etc through the use of matcher methods.

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Q19. Can you name few matchers that can be used with hamcrest assertThat method ?

Junit

Ans. is
not
equals
anyOf
hasSize

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Q20. What are the benefits of Junits ?

Junit

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Q21. What is doCallRealMethod() method used for ?

PowerMock

Ans. When we Mock an object and then make a reference to any method using mocked object reference , java never makes a call to that method and looks for mocked value to be returned or null if none specified. But If we want that to be overridden and want java to make actual method call upon using mocked object reference, this method can be used.

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Q22. What is a difference between JUnit 3 and 4 ?

Junit

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Q23. How to find if any employees address is null or not during Junit testing

JUnit

Ans. By using assertNotNull(employee_address)

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Q24. How do you test object construction or constructors using junit ?

Junit

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Q25. What are the points to consider while reviewing junits ?

Junit

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Q26. Can we pass the junit test if the tested method throws the exception ? and Should we do that ?

Junit

Ans. Yes, We can pass the test even if the tested method throws an exception.

One way is know as exception testing in which the tested method is expected to throw exception and hence the expectation is set accordingly.

@Test(expected = IndexOutOfBoundsException.class)
public void test(){}

Other way is to just ignore if the tested code throws an exception. In that case , we can enclose the tested method call in the try block and within exception block, we just return gracefully.

Exception testing is perfectly ok to be done as we would like test code in case an exception occurs and if the code is handling the exception properly. Ignoring the exception by putting the tested method call within try block isn't something normal and should be avoided.

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Q27. Write a unit test case using java 8.

JUnit

Ans. public List convertAllToUpperCase(List words) {
return words.stream().map(String::toUpperCase).collect(Collectors.toList());
}

@Test
public void testAllToUpperCase() {
List expected = Arrays.asList("JAVA8", "STREAMS");
List result = convertAllToUpperCase(Arrays.asList("java8", "streams"));
assertEquals(expected, result);
}

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Q28. What does this warning message for the unit test means

WARN: 'Spec has no expectations.'

Angular

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Q29. Which of following annotation is used to initialize objects before executing set of tests ? Reference

Junit

a. @Test

b. @Ignore

c. @After

d. @Before

Ans.d. @Before

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