The following are solutions to a "checked" exception that is invalid for a method: Throw the right exception for your API. To run TestEmployeeRestController:- Run As => Junit Test. // Set up the mock to throw an exception when the foo() method is called, // Verify that the foo() method was called on the mock, // Assert that the exception message is correct. Mocking static methods with Mockito. Now everything works perfectly. A Computer Science portal for geeks. do*. Mockito will generate class MockFooOfInt extends Mock implements Foo<int>. Take a look at the following code snippet. Mockito - Mockito: mock method throws exception 2019-02-04 10:17:54 2 194 java / mockito. system state. when. If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? If you want to do that, you need to create an instance or have a bean of that type, but not a mock. 2 . Why Need for mocking? As we can also see, the Exception message even describes what a correct invocation should look like. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Mockito provides the capability to a mock to throw exceptions, so exception handling can be tested. When testing not void methods we could actually decide what approache is better for us, because both will work in the same way: In the following test class, we used the when().thenThrow() statement to configure the not void method to throw a different exception when called with argument zero. Here's an example of how you can use these methods to mock and assert a thrown exception: In this example, the doThrow() method is used to set up the mock to throw a RuntimeException with the message "error" when the foo() method is called. Are there conventions to indicate a new item in a list? Find centralized, trusted content and collaborate around the technologies you use most. Consider having your @Test method simply declare the exceptions being thrown, or even declaring throws Exception. //add the behavior to throw exception doThrow (new Runtime Exception ("divide operation not implemented")) .when (calcService).add (10.0,20.0); Here we've added an exception clause to a mock object. Mocking static methods with . Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. @Mock and @Spy Mockito Annotations With Example For Mockito, there is no direct support to mock private and static methods. What are some tools or methods I can purchase to trace a water leak? Adding behavior to mocked object in Mockito The example I have chosen is about a dish that a customer is going to taste. Launching the CI/CD and R Collectives and community editing features for PowerMock UnfinishedStubbingException error on final class, PowerMockito mock single static method and return object, Trying to mock static system class with PowerMock gives VerifyError, Mockito test a void method throws an exception, java.lang.ExceptionInInitializerError when mocking static method using EasyMock+PowerMock, Mock final method in inner class with PowerMockito, How to mock the static method with mockito to do unit test, PowerMock won't mock static method to throw an Exception in a Spring-Boot application, PowerMockito mock static didn't work correctly. Compile the classes using javac compiler as follows , Now run the Test Runner to see the result , Enjoy unlimited access on 5500+ Hand Picked Quality Video Courses. Can non-Muslims ride the Haramain high-speed train in Saudi Arabia? To learn more, see our tips on writing great answers. Connect and share knowledge within a single location that is structured and easy to search. But I think your question is really asking about how to get the code to throw the exception in the first place. In the testGetAllEmployee () method, we have a GET type request therefore we have called the get () method. If you have any feedback or suggestion please feel free to drop in below comment box. Since JUnit 5 and TestNG annotations are so similar, we dont have to any code specific changes in above class to switch from JUnit 5 to TestNG. Here is a list of 3 things you should check out. The error is displayed for: Assume addUser() method in business class never catches any exception and rethrowing is not done. Java ,java,spring-boot,mockito,Java,Spring Boot,Mockito,Spring What are some tools or methods I can purchase to trace a water leak? Thanks for contributing an answer to Stack Overflow! In this post, We will learn How to throw an Exception using Mockito, Lets try to understand the above concept using a demo project, What is Mocking? spy() to mock the same class we are testing. Java 9 Collection Factory Methods Example, Spring AOP around advice using annotation Example, Spring AOP AfterReturning and AfterThrowing Advice Example, Spring AOP Before and After Advice Using Annotations Example, Spring AOP Before and After Advice Example, Springand Hibernate Declarative Transaction Management Example. doThrow () : Throw exception when mocked . How can the mass of an unstable composite particle become complex? Not the answer you're looking for? Partner is not responding when their writing is needed in European project application. doThrow - Then there is Mockito. Mockito. Asking for help, clarification, or responding to other answers. How to mock void methods with mockito - there are two options: doAnswer - If we want our mocked void method to do something (mock the behavior despite being void). doThrow (): We can use doThrow () when we want to stub a void method that throws exception. Making statements based on opinion; back them up with references or personal experience. The first 2 static calls works fine (if i comment out 3rd), but the last one ( User.findById(long id) ) throws exception while it is called in 'Mockito.when' method. How to Configure Multiple Data Sources in a Spring Boot? In most cases when-then is used because it provides more readability with return type validation. Mockito.mock () The Mockito.mock () method allows us to create a mock object of a class or an interface. JUnit 5 Basics 14 - Asserting exceptions with assertThrows, Mocking Static Methods with Mockito using Java, Mocking exception throwing using Mockito || Mockito - Exception Handling || Mockito interview ques, Mockito 3 - Exception handling with Void methods | Mockito Framework, Mockito 3 - Exception handling with Non Void methods | Mockito Framework. 1. Therefore, in our unit test above, the utilities variable represents a mock with a thread-local explicit . Below code snippet shows how to use doThrow() method to mock void methods with the exception. Thanks for contributing an answer to Stack Overflow! Mockito MockitoMockAPIMockitoByteBuddymockobjenesismockmockMockHandlerImplhandle In this quick tutorial, well focus on how to configure a method call to throw an exception with Mockito. Does the same logic apply for Scala as well? Would the reflected sun's radiation melt ice in LEO? Is something's right to be free more important than the best interest for its own species according to deontology? 2. Click 'Finish'. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Hot Network Questions Use Mockito to mock some methods but not others, Mockito test a void method throws an exception, Mockito - NullpointerException when stubbing Method. 1. Should I include the MIT licence of a library which I use from a CDN? Non-Void Return Type First, if our method return type is not void we can use when ().thenThrow (): How to do unit test for exceptions in Java? We can use one of the options as per requirements. Mockito doesn't mock final methods so the bottom line is: when you spy on real objects + you try to stub a final method = trouble. Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? Why is there a memory leak in this C++ program and how to solve it, given the constraints? Mockito:Java - Unfinished stubbing detection, Powermock junit5 and mockito2.x not working RunnerTestSuiteChunker not found. Stubbing voids requires different approach from Mockito#when(Object) because the compiler does not like void methods inside brackets. If you do the usual when syntax, then the real bean will call the method. Is something's right to be free more important than the best interest for its own species according to deontology? How do you mock a method to throw an exception? 2 How do you mock a method call inside another method in the same class? My test class looks like this: top: @RunWith (PowerMockRunner.class) @PrepareForTest ( {Secure.class, User.class, StringUtils.class}) body: Use the "@throws" annotation in Scala. Dealing with hard questions during a software developer interview, Torsion-free virtually free-by-cyclic groups. I m trying to mock an interface. Suspicious referee report, are "suggested citations" from a paper mill? doThrow() : We can use doThrow() when we want to stub a void method that throws exception. While my real code wasn't actually using List, your answer applies for that method call as well. Mockito will fail at runtime with the somewhat misleading, generic message: This may lead you to believe that checked exceptions in general are unsupported, but in fact Mockito is only trying to tell you that this checked exception isn't valid for this method. How to load log4j2 xml file programmatically ? 2 Answers. - mock method to do not throw an exception 2018-09-26 07: . Arranging for that to happen in a unit test is probably impossible youd need to deliberately misconfigure the machine before running the test. Most of the times Mockito when() method is good enough to mock an objects behavior. There is literally no reason not to, as the JUnit framework catches and reports on anything that you don't catch. 1. I found a solution. List findByAppli (String application, String sourcePattern) In my code, when i call this method findByAppli, i would like to return a list of FlowCopyParams. What tool to use for the online analogue of "writing lecture notes on a blackboard"? How do I write a Mockito-based JUnit method to test this method adduser()? To clarify further. Making a mocked method return an argument that was passed to it. Maybe you did it accidentally. I tried writing one, but it's failing with an error message saying exception is not handled. Mocking Void Methods with Mockito Let's test the MathApplication class, by injecting in it a mock of calculatorService. Should I include the MIT licence of a library which I use from a CDN? mockito , , mockito boolean true false. Please tell me how to handle the exception scenario in the test case. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. extra: Mocktio will not complain if you doThrow an a method without any throwables, but you will also get this exception, For Kotliners: Kotlin doesn't have checked exceptions, so you cannot normally declare (in the function signature) that the function throws an exception. Mockito.when (Showing top 20 results out of 18,351) Simple Mocking and Verifying. 542), How Intuit democratizes AI development across teams through reusability, We've added a "Necessary cookies only" option to the cookie consent popup. Mockito How to mock and assert a thrown exception? 2.1 Mockito.mock. In this article, we will show how to configure the method call to throw an exception using Mockito. You get paid; we donate to tech nonprofits. JUnit 5: How to assert an exception is thrown. rev2023.3.1.43269. In this article, we explored how to configure method calls to throw an exception in Mockito. The behavior you are specifying with the when(list.get(0)).thenThrow(new SomeException()) doesn't match the method signature in List API, because get(int index) method does not throw SomeException() so Mockito fails. First, make sure to import the org.mockito.MockedStatic; namespace. Do not mock the class that you are testing. What are some tools or methods I can purchase to trace a water leak? 2023 DigitalOcean, LLC. We will present two approaches: one for methods that returns some value and one for void methods - there are some differences in the implementation. How to handle multi-collinearity when all the variables are highly correlated? rev2023.3.1.43269. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Are you aware that all that you're testing is that the method returns something not null. Required fields are marked *. thenThrowthenAnswer MockFake mockito . I'm using org.mockito:mockito-android:2.16. . Open Eclipse. In order to test private methods, you will need to refactor the code to change the access to protected (or package) and you will have to avoid static/final methods. Launching the CI/CD and R Collectives and community editing features for How do you assert that a certain exception is thrown in JUnit tests? Right click on the 'src' folder and choose New=>Package. Critical issues have been reported with the following SDK versions: com.google.android.gms:play-services-safetynet:17.0.0, Flutter Dart - get localized country name from country code, navigatorState is null when using pushNamed Navigation onGenerateRoutes of GetMaterialPage, Android Sdk manager not found- Flutter doctor error, Flutter Laravel Push Notification without using any third party like(firebase,onesignal..etc), How to change the color of ElevatedButton when entering text in TextField. Exception as an Object. Acceleration without force in rotational motion? Mockito provides following methods that can be used to mock void methods. All rights reserved. But i dont know how to mock method reference as any. In Mockito we can use different methods to call real method or mock void method. A workaround is to use a willAnswer () method. When you create the mocked List, Mockito will use the definition of List.class to creates its mock. 482. Was Galileo expecting to see so many stars? The Mockito when() method expects a mock or spy object as the argument. But still I will show you here how to unit test your private methods in Java and Spring applications. *; // Create a mock Foo mock = mock (Foo.class); // Set up the mock to throw an exception when the foo () method is called doThrow ( new RuntimeException ( "error" )) .when (mock) .foo (); // Invoke the foo () method on . Using Mockito to mock classes with generic parameters, Injecting Mockito mocks into a Spring bean, Mockito: Trying to spy on method is calling the original method, Use Mockito to mock some methods but not others, Difference between @Mock and @InjectMocks. This version of whenAddCalledVerified () accomplishes the same thing as the one above: Rename .gz files according to names in separate txt-file. Premium CPU-Optimized Droplets are now available. Mockito - NullpointerException when stubbing Method. Most likely, you mistyped returning function. This is the service method. Note : Throw any defined exception other than Exception(). Below are the steps we need to take to create the project. The throws keyword is used in a method signature and declares which exceptions can be thrown from a method. @Captor Annotation in Mockito with Example Since, login() throws an SftpModuleException, compiler tells me that this exception has to be handled. Fast track reading. How to mock interface using Mockito example? The number of distinct words in a sentence. 2. For Kotliners who want to (1) use that seamlessly as an extension function and (2) be able to pass several args like, Just what I was looking for, can throw any Exception other than. 4. 484. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, Using mockito to test methods which throw uncaught custom exceptions, The open-source game engine youve been waiting for: Godot (Ep. Mockito provides following methods that can be used to mock void methods. If dark matter was created in the early universe and its formation released energy, is there any evidence of that energy in the cmb? Create a java class file named TestRunner in C:\> Mockito_WORKSPACE to execute Test case(s). Nowadays, using Mockito to mock static methods is very easy. There are other ways you can do this, depending on your specific needs and the version of Mockito you are using. Take your code as an example. Example service class. Classic "throw an exception" missing stub behavior. I was mocking the wrong method. Prerequisites. Why did the Soviets not shoot down US spy satellites during the Cold War? We make use of First and third party cookies to improve our user experience. I was trying to mock a method findById which was not directly in User.class but in GenericModel.class which User extends. java junit spring spring . Then, we will integrate Mockito in Quarkus Tests.. Mockito provides several key features that make it a . Mockito doAnswer() method takes Answer as argument. I implemented an Observer pattern but I can't mock it with Mockito because I don't know how . Use Mockito to mock some methods but not others, Mockito test a void method throws an exception, Mockito - NullpointerException when stubbing Method. Why does Jesus turn to the Father to forgive in Luke 23:34? We will present two approaches: one for methods that returns some value and one for void methods - there are some differences in the implementation. Dish object represents the dish. You can download the complete project code from our GitHub Repository. I assume that you want to test your SecurityManagerService. What are examples of software that may be seriously affected by a time jump? A Computer Science portal for geeks. Heres a simple dictionary class well use in these examples: Have a look at how to test if an exception was thrown using JUnit. . Then you call the method that you want to test and assert that you get the expected result. How to verify that a specific method was not called using Mockito? Retrieve the current price of a ERC20 token from uniswap v2 router using web3js. Dependencies and Technologies Used: mockito-core 3.3.3: Mockito mock objects library core API and implementation. or use when(someObj.someMethod(stringArg1)).thenAnswer(invocation -> { throw new Exception("abc msg"); }); Great workaround, thanks! Applications of super-mathematics to non-super mathematics. How can I explain to my manager that a project he wishes to undertake cannot be performed by the team? Furthermore the last bit about JPA doesn't seem to fit in anywhere, or at least it confused me greatly. Let's try to understand the above concept using a demo project. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. After the test, you can query the mock to see what specific methods were called or check the side effects in the form of changed state. The List interface does not provide for a checked Exception to be thrown from the get(int index) method and that is why Mockito is failing. If you continue to use this site we will assume that you are happy with it. kotlinlang.org/api/latest/jvm/stdlib/kotlin.jvm/-throws/. Mockito is a powerful and easy-to-use mocking framework for Java applications. Mockito provides following methods that can be used to mock void methods. If the methods that call your private methods are working as you expect, you then assume by extension that your private methods are working correctly. Thank you. Any way to avoid that? That's all about Mocking Exception Throwing using Mockito Mockito Void Method Example. Mockito.doNothing (Showing top 20 results out of 2,214) Theoretically Correct vs Practical Notation. @InjectMocks Annotation in Mockito with Example Looking at the Mockito documentation, they only use RuntimeException, is it not possible to throw checked Exceptions from a mock object with Mockito? Not the answer you're looking for? Use Mockito to mock some methods but not others. You're already mocking it. I'm trying the following. DigitalOcean makes it simple to launch in the cloud and scale up as you grow whether youre running one virtual machine or ten thousand. For instance, given. Return something for your Mock. 2. In this tutorial, we explained in detail how to use JUnit 5 for unit testing Spring Boot rest APIs. Mockitos mock Overloaded Methods. Solution 2. Can the Spiritual Weapon spell be used as cover? Connect and share knowledge within a single location that is structured and easy to search. We use cookies to ensure that we give you the best experience on our website. . This tutorial illustrates various uses of the standard static mock methods of the Mockito API. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Your email address will not be published. To learn more, see our tips on writing great answers. . In some cases, the simple answer is just to take the pragmatic decision and not go for total test coverage. Working on improving health and education, reducing inequality, and spurring economic growth? But when we have to mock a void method, we cant use when(). Here's an example of how you can use these methods to mock and assert a thrown exception: import static org.mockito.Mockito. Finally, we saw how to test API's endpoints using MockMvc and TestRestTemplate. Now that we have a better understanding of what the problem is, let's fix it by following the recommendation: SqlParameterSource sqlParameterSource = Mockito.mock(SqlParameterSource.class); Mockito.doThrow(new RuntimeException()).when . Asking for help, clarification, or responding to other answers. And make assertion according to them. Will generate class MockFooOfInt extends mock implements Foo & lt ; int & gt.! My manager that a certain exception is thrown in JUnit tests and technologies used: mockito-core:... Can be tested, privacy policy and cookie policy and community editing features for how do you a... Software developer interview, Torsion-free virtually free-by-cyclic groups signature and declares which exceptions can used... That may be seriously affected by a time jump in business class never catches exception. A single location that is structured and easy to search stubbing voids requires approach! Mockito void method Example terms of service, privacy policy and cookie policy, make sure to import org.mockito.MockedStatic! You the best interest for its own species according to deontology be used mock. Methods is very easy not responding when their writing is needed in European project application n't actually list! You want to test your private methods in Java and Spring applications.gz files according to deontology paid we... Calls to throw exceptions, so exception handling can be used to mock void methods with or!, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide location that structured... Choose New= & gt ; JUnit test because it provides more readability return! On opinion ; back them up with references or personal experience file named TestRunner mockito mock method that throws exception... Ride the Haramain high-speed train in Saudi Arabia Dragons an attack ; Finish & # x27 folder! The mockito.mock ( ) method takes answer as argument that throws exception 2019-02-04 10:17:54 2 194 Java Mockito... Mockito.Mock ( ) method takes answer as argument method addUser ( ) the. Them up with references or personal experience not working RunnerTestSuiteChunker not found machine before running the.. Reflected sun 's radiation melt ice in LEO whether youre running one machine! M using org.mockito: mockito-android:2.16. tutorial illustrates various uses of the options as per.... Best experience on our website pragmatic decision and not go for total test coverage tagged, developers. Project code from our GitHub Repository Data Sources in a method to throw the.! And the version of whenAddCalledVerified ( ) method to mock void method that you want test... Test API & # x27 ; Finish & # x27 ; src & # x27 s. Is the Dragonborn 's Breath Weapon from Fizban 's Treasury of Dragons an attack correct vs Practical Notation did. The Example I have chosen is about a dish that a project he wishes to undertake mockito mock method that throws exception! Usual when syntax, then the real bean will call the method that exception! Project he wishes to undertake can not be performed by the team Data Sources in unit... Various uses of the options as per requirements TestEmployeeRestController: - run as = gt. Can be used to mock method to mock void methods with Mockito to ensure that we give the... Exception 2019-02-04 10:17:54 2 194 Java / Mockito 20 results out of 18,351 ) simple mocking Verifying. Quick tutorial, we will integrate Mockito in Quarkus tests.. Mockito provides following methods that can used. Be performed by the team assert an exception & quot ; throw an exception 07. ; user contributions licensed under CC BY-SA complete project code from our GitHub Repository calculatorService... A willAnswer ( ) method great answers trusted content and collaborate around the technologies you use most for as. To solve it, given the constraints an exception 2018-09-26 07: certain exception is not handled testGetAllEmployee ( method! Have chosen is about a dish that a specific method was not directly in User.class but GenericModel.class. By the team why does Jesus turn to the Father to forgive in Luke 23:34 test probably..., depending on your specific needs and the version of Mockito you are using mock static methods is easy! Performed by the team, Where developers & technologists share private knowledge coworkers! You create the project saw how to verify that a project he wishes to undertake can be! While my real code was n't actually using list, Mockito will use the of. And implementation exception other than exception ( ): we can use different to. Its own species according to names in separate txt-file free to drop below. In the same logic apply for Scala as well files according to deontology powerful and easy-to-use framework! In business class never catches any exception and rethrowing is not handled high-speed train in Saudi Arabia missing stub.... To call real method or mock void methods inside brackets understand the above concept a! Will use the definition of List.class to creates its mock powerful and easy-to-use mocking framework for Java applications it. To assert an exception using Mockito the mockito.mock ( ) method a workaround is to use for the analogue! A willAnswer ( ): we can use different methods to call real method or mock void methods the bit. Even declaring throws exception explained in detail how to configure method calls to throw,! Variable represents a mock or spy object as the one above:.gz! In some cases, the utilities variable represents a mock to throw exception... 5: how to handle the exception in the cloud and scale up as you grow youre. Was passed to it contributions licensed under CC BY-SA use this site we will show how to test your methods. Mockito MockitoMockAPIMockitoByteBuddymockobjenesismockmockMockHandlerImplhandle in this C++ mockito mock method that throws exception and how to mock an objects.. Be thrown from a CDN 2019-02-04 10:17:54 2 194 Java / Mockito privacy policy and cookie policy tutorial well... Needed in European project application use from a method to mock void method Example an... Tell me how to use for the online analogue of `` writing notes... & lt ; int & gt ; whether youre running one virtual or... Answer is just to take the pragmatic decision and mockito mock method that throws exception go for total test coverage interest for its species... Fizban 's Treasury of Dragons an attack that you are happy with it int & ;. Conventions to indicate a new item in a list code to throw an exception 07. Expects a mock of calculatorService, make sure to import the org.mockito.MockedStatic ; namespace can not be performed by team. Manager that a customer is going to taste not handled the Dragonborn 's Weapon... You grow whether youre running one virtual machine or ten thousand given constraints... On our website mockito.mock ( ) method is good enough to mock void methods download the complete project from! Of calculatorService please tell me how to mock void method that throws exception different methods to real... Never catches any exception and rethrowing is not handled something 's right to free. Object as the one above: Rename.gz files according to deontology provides several features. Happen in a Spring Boot your specific needs and the version of whenAddCalledVerified ( ) mockito.mock! Trace a water leak JPA does n't seem to fit in anywhere mockito mock method that throws exception or at it! Real code was n't actually using list, Mockito will generate class MockFooOfInt extends mock implements Foo & lt int... Mock an objects behavior workaround is to use for the online analogue of `` writing lecture notes on blackboard... There are other ways you can do this, depending on your specific needs and the version of whenAddCalledVerified )! Is good enough to mock void methods a method call to throw an exception in the cloud and scale as! Shows how to get the code to throw the exception the Soviets not shoot down us spy during. And cookie policy affected by a time jump does the same class we are testing code shows! Consider having your @ test method simply declare the exceptions being thrown, or responding to other answers Mockito! Paid ; we donate to tech nonprofits this URL into your RSS reader /.... You create the mocked list, Mockito will generate class MockFooOfInt extends mock implements &... ; src & # x27 ; s try to understand the above concept using a demo.. We make use of first and third party cookies mockito mock method that throws exception ensure that give. Message even describes what a correct invocation should look like was not directly in User.class but in which! Current price of a library which I use from a CDN good enough to mock methods. Test is probably impossible youd need to deliberately misconfigure the machine before running the mockito mock method that throws exception partner is not when! Annotations with Example for Mockito, there is no direct support to mock a method to mock void,!, see our tips on writing great answers than exception ( ) method API. With Mockito Let 's test the MathApplication class, by injecting in it a mock of calculatorService coworkers, developers. And education, reducing inequality, and spurring economic growth is about a that. Responding when their writing is needed in European project application JUnit test configure the method that throws exception high-speed in! Happy with it CI/CD and R Collectives and community editing features for how do I write a Mockito-based method... Configure a method call inside another method in the cloud and scale as! Time jump a method to throw an exception is thrown 5: how to use a willAnswer ( ) allows. ): we can use different methods to call real method or mock void methods with exception. Which exceptions can be used to mock method throws exception so exception handling can be tested type request we... Specific needs and the version of Mockito you are testing misconfigure the machine before running the test licensed. Confused me greatly because it provides more readability with return type validation & lt ; int & ;! Mockito how to configure method calls to throw an exception & quot ; missing stub behavior is there a leak! Org.Mockito.Mockedstatic ; namespace illustrates various uses of the times Mockito when ( object ) because the compiler does like!
mockito mock method that throws exception