Top 100+ Mockito Interview Questions And Answers
Question 1. What Is Mockito?
Answer :
Mockito lets in introduction of mock object for the reason of Test Driven Development and Behavior Driven improvement. Unlike growing actual item, Mockito allows creation of fake object (outside dependencies) which allows it to give regular outcomes to a given invocation.
Question 2. Why Do We Need Mockito? What Are The Advantages?
Answer :
Mockito differentiates itself from the alternative checking out framework through eliminating the expectation in advance. So, with the aid of doing this, it reduces the coupling. Most of the trying out framework works on the "assume-run-confirm". Mockito lets in it to make it "run-verify" framework. Mockito additionally gives annotation which lets in to lessen the boilerplate code.
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Question 3. Can You Explain A Mockito Framework?
Answer :
In Mockito, you always test a selected class. The dependency in that class is injected the usage of mock item. So, for example, if you have service elegance, then the Dao elegance are injected as a mockDao. This allows us to test only the technique of that given carrier magnificence and whether they're performing as predicted or not.
For instance, suppose, carrier elegance has an updateObject Method. That update method is rely on Dao1, Dao2. Here the goal is to test best the updateObject method and now not the Dao1 and Dao2. So, we will create a mockDao and return a ridicule item. This item is not the only that's in the database however is custom made. It handiest tests whether the updates are going on as anticipated or no longer. The syntax to create a Mock item is as follows:
non-public static LedgerBook mockLedgerBook;
In the setup(), you create the mock object
setup()
mockLedgerBook = Mockito.Mock(LedgeBookDao.Magnificence);
In the test method, you name this mockLedgerBook as follows:
LedgerBook ledgerBook = new LedgerBook();
ledgerBook.SetName("default");
Mockito.While(mockLedgerBook.FindBookById(Mockito.AnyLong()).ThenReturn(ledgerBook);
Question 4. What Is The Version You Used For Mockito Framework?
Answer :
1.9.Five version of Mockito.
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Question five. How Do You Create A Mockdb Object In Mockito?
Answer :
We need to create the mock object and want to skip the invocation. We have to override the approach in the real DB with the approach over here and pass the reaction object.
Mockito.While(mockObjectDao.Locate((Guid) Mockito.AnyObject())).ThenAnswer(new Answer<responseObject>()
@Override
public responseObject solution(InvocationOnMock invocation) throws Throwable
Guid responseObjectID = (Guid) invocation.GetArguments()[0];
responseObject responseDbObject = new responseObject();
responseDbObject.SetresponseObjectId(responseObjectID);
responseObjectLink responseObjectLink = new responseObjectLink();
responseObjectLink.SetLedgerBookId(Guid.CreateGuid());
responseObjectLink.SetresponseObjectId(responseObjectID);
responseObjectLink.SetLedgerObjectId(Guid.CreateGuid());
responseDbObject.GetresponseObjectLinks().Add(responseObjectLink);
for (Contact sourceContact : responseObjectDTO.GetSourceContacts())
if (!SourceContact.GetObjectId().Equals(responseObjectID))
responseObjectLink = new responseObjectLink();
responseObjectLink.SetLedgerBookId(sourceContact.GetAddressBookId());
responseObjectLink.SetresponseObjectId(responseObjectID);
responseObjectLink.SetLedgerObjectId(sourceContact.GetObjectId());
responseDbObject.GetresponseObjectLinks().Upload(responseObjectLink);
go back responseDbObject;
);
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Question 6. Which Of The Following Are Usually Automated And Which Are Executed Manually ?
1. Unit Test
2. Integration Test
Answer :
Unit Test are normally automated and Integration Tests are generally done manually.
Question 7. What Are Junits ?
Answer :
Junt is the unit testing framework for Java.
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Question 8. Are Junits Tested Manually?
Answer :
No , they're accomplished automatically.
Question nine. How To Test Whether The Returns Value Of The Method Is Expected ?
Answer :
Using Assert.
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Question 10. What Happens If The Assert Doesn't Evaluate To Be True ?
Answer :
Junit fails.
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Question 11. How To Create A Junit To Make Sure That The Tested Method Throws An Exception ?
Answer :
Using annotation Test with the argument as predicted exception.
@Test (anticipated = Exception.Elegance)
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Question 12. What Should I Do If I Want To Make Sure That A Particular Method Of A Class Is Getting Called?
Answer :
If its a static method of the class , we are able to use affirm to make certain it's getting referred to as.
If its an instance method , We can mock the object after which use affirm with the mocked object to ensure that the method is getting referred to as."
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Question thirteen. Name Few Java Mocking Frameworks?
Answer :
Mockito, PowerMock, EasyMock, JMock, JMockit
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Question 14. What Is The Use Of Mockito.Any?
Answer :
In case we need to verify that a method is being referred to as with any argument and now not a selected argument we will use Mockito.Any(Class), Mockito.AnyString, Mockito.AnyLong and so on.
Question 15. How Should We Ignore Or Avoid Executing Set Of Tests ?
Answer :
We can get rid of @Test from the respective take a look at with a view to avoid its execution. Alternatively we can positioned @Ignore annotation at the Junit file if we want to disregard all checks in a specific report.
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Question sixteen. How Can We Test Methods Individually Which Are Not Visible Or Declared Private ?
Answer :
We can both boom their visibility and mark them with annotation @VisibleForTesting or can use mirrored image to for my part take a look at the ones techniques.
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Question 17. Is It Really A Mocking Framework?
Answer :
There is a piece of confusion across the vocabulary. Technically speaking, Mockito is a Test Spy framework. Usually builders use Mockito rather than a mocking framework. Test Spy framework lets in to confirm behaviour (like mocks) and stub methods (like suitable old handmade stubs).
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Question 18. Why Is Mockito So Simple?
Answer :
To sell easy test code that with a bit of luck pushes the developer to jot down easy and clean utility code. I wrote this paragraph lengthy earlier than version 1.5. Mockito continues to be quite lean however the variety of capabilities accelerated because many users located legitimate cases for them.
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Question 19. What Are The Limitations Of Mockito?
Answer :
Mockito 2.X unique obstacles
Requires Java 6+
Cannot mock static techniques
Cannot mock constructors
Cannot mock equals(), hashCode(). Firstly, you ought to not mock the ones strategies. Secondly, Mockito defines and relies upon upon a particular implementation of these techniques. Redefining them would possibly spoil Mockito.
Mocking is most effective feasible on VMs which are supported with the aid of Objenesis. Don't fear, most VMs must work simply first-class.
Spying on real methods in which real implementation references outer Class through OuterClass.That is impossible. Don't worry, this is extraordinarily uncommon case.
Mockito 1.X Specific obstacles
Needs Java five+
Cannot mock final classes
Cannot mock final methods - their real conduct is executed without any exception. Mockito can't warn you approximately mocking very last methods so be vigilant.
Cannot mock static strategies
Cannot mock constructors
Cannot mock equals(), hashCode(). Firstly, you have to no longer mock those techniques. Secondly, Mockito defines and depends upon a selected implementation of those strategies. Redefining them would possibly destroy Mockito.
Mocking is only viable on VMs which might be supported via Objenesis (Note Objenesis is in model 2.1). Don't worry, most VMs ought to work simply fine.
Spying on actual strategies where actual implementation references outer Class through OuterClass.This is impossible. Don't worry, that is extremely uncommon case.
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Question 20. Do You Mock Classes & Interfaces?
Answer :
Yes, the api is the same for mocking training or interfaces.
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Question 21. What Values Do Mocks Return By Default?
Answer :
In order to be obvious and unobtrusive all Mockito mocks via default go back 'high-quality' values. For example: zeros, falseys, empty collections or nulls. Refer to javadocs approximately stubbing to look exactly what values are back by default.
Question 22. Can I Mock Static Methods?
Answer :
No. Mockito prefers item orientation and dependency injection over static, procedural code this is tough to apprehend & alternate. If you cope with horrifying legacy code you could use JMockit or Powermock to mock static strategies.
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Question 23. Can I Mock Private Methods?
Answer :
No. From the standpoint of testing... Personal methods do not exist.
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Question 24. Is Mockito Thread-safe?
Answer :
For wholesome scenarios Mockito performs nicely with threads. For instance, you may run assessments in parallel to hurry up the build. Also, you can let more than one threads name strategies on a shared mock to check in concurrent situations. Check out a timeout() function for testing concurrency.
However Mockito is simplest thread-secure in wholesome assessments, this is exams without more than one threads stubbing/verifying a shared mock. Stubbing or verification of a shared mock from distinct threads is NOT the right way of testing because it will continually cause intermittent behavior. In standard, mutable nation + assertions in multi-threaded surroundings result in random consequences. If you do stub/verify a shared mock across threads you may face occasional exceptions like: WrongTypeOfReturnValue, and many others.
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Question 25. Can I Verify Tostring()?
Answer :
No. You can stub it, even though. Verification of toString() isn't implemented particularly because:
When debugging, IDE calls toString() on gadgets to print neighborhood variables and their content material, etc. After debugging, the verification of toString() will maximum in all likelihood fail.
ToString() is used for logging or throughout string concatenation. Those invocations are usually inappropriate however they may exchange the outcome of verification.
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Question 26. Can I "reset" A Mock?
Answer :
Recently we determined to move on with this option for complex eventualities where mocks are created by using the field. Before that, the dearth of a reset approach turned into consider to sell good checking out habits and to make the API less complicated.
Instead of reset() please take into account writing easy, small and centered take a look at strategies over lengthy, over-particular checks.
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Question 27. What Are Unfinished Verification/stubbing Errors?
Answer :
Mockito validates if you use it efficaciously all the time. Examples of wrong use:
//Oups, someone forgot thenReturn() component:
when(mock.Get());
//Oups, a person put the tested method name inner confirm() wherein it must be out of doors:
verify(mock.Execute());
//Oups, someone has used EasyMock for too long and forgot to specify the method to affirm:
verify(mock);
Mockito throws exceptions if you misuse it so you will realize if your checks are written effectively. The best problem is that Mockito does the validation subsequent time you use the framework. Therefore every now and then the exception is thrown in the next check and you need to manually discover the previous test that became no longer written effectively.
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Question 28. Why Does Mockito Keep Threadlocal State?
Answer :
Mockito makes use of ThreadLocal country to put into effect a suitable mocking syntax in a language complete of constraints (sure, it's java). Fortunately, on every occasion you interact with Mockito framework it validates the ThreadLocal nation if you misused the api.
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Question 29. Can I Thenreturn() An Inlined Mock() ?
Answer :
Unfortunately you can not do that:
when(m.Foo()).ThenReturn(mock(Foo.Elegance));
// ^
The reason is that detecting unfinished stubbing wouldn't paintings if we permit above assemble. We recollect this as a 'trade off' of framework validation (see additionally previous FAQ access). However you may barely trade the code to make it working:
//extract local variable and start smiling:
Foo foo = mock(Foo.Magnificence);
whilst(m.Foo()).ThenReturn(foo);
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Question 30. Can I Stub Chained Getters?
Answer :
kind of stubbing, e.G. Mock to go back mock, to go back mock, and so on. Need to be used very sporadically, preferably never. It simply points out violation of the Law of Demeter. You do not want to clutter with Demeter. Since you have got been warned take a look at out Mockito deep stubs.
Question 31. Will This Library Help Mocking Closed (non-open) Classes?
Answer :
Mockito-Kotlin does not clearly add any greater capability to Mockito. As such, you will nevertheless get exceptions while trying to mock closed instructions. If feasible, try to use interfaces as a substitute.
Mockito gives an incubating, opt-in function to permit mocking closed training.
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Question 32. Will This Library Help Overcoming Nullpointerexceptions With Mockito.Any()?
Answer :
Passing Mockito.Any() to a non-nullable parameter in Kotlin fails with a NullPointerException. Mockito-Kotlin attempts to triumph over this.
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Question 33. I Get An Error ‘resolved Versions For App (1.1.X) And Test App (1.Zero.X) Differ’. What Should I Do?
Answer :
Mockito-Kotlin relies upon on model 1.0.X of Kotlin’s fashionable and reflect library. If you rely on 1.1.X, you may get this error. To resolve this, upload the following snippet on your root’s construct.Gradle, changing $kotlinVersion with the model your mission uses:
subprojects
configurations.All
resolutionStrategy
forcedModules = [
"org.Jetbrains.Kotlin:kotlin-stdlib:$kotlinVersion",
"org.Jetbrains.Kotlin:kotlin-reflect:$kotlinVersion"
]
If you don’t want to force dependencies like this, you can alternatively depend upon the more recent version of kotlin-reflect explicitly, if you want to make Mockito-Kotlin use that model as well:
testCompile 'com.Nhaarman:mockito-kotlin:x.X.X`
testCompile 'org.Jetbrains.Kotlin:kotlin-mirror:1.1.1'
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Question 34. Will This Library Support Mockito 1.X?
Answer :
No. Mockito 2.X is formally launched and this library will awareness on those variations.
Question 35. When Will This Library Reach 1.Zero.Zero?
Answer :
Mockito-Kotlin reached 1.0.Zero December 6th. Try it out!
