throw checked Exceptions from mocks with Mockito

Question

I m trying to have one of my mocked objects throw a checked Exception when a particular method is called  I m trying the following    Test expectedExceptions   SomeException class  public void throwCheckedException         List lt String gt  list   mock List class       when list get 0   thenThrow new SomeException         String test   list get 0      public class SomeException extends Exception       However  that produces the following error   org testng TestException   Expected exception com testing MockitoCheckedExceptions SomeException but got org mockito exceptions base MockitoException   Checked exception is invalid for this method  Invalid  com testing MockitoCheckedExceptions SomeException   Looking at the Mockito documentation  they only use RuntimeException  is it not possible to throw checked Exceptions from a mock object with Mockito

User · Accepted Answer

Check the Java API for List  The get int index  method is declared to throw only the IndexOutOfBoundException which extends RuntimeException  You are trying to tell Mockito to throw an exception SomeException   that is not valid to be thrown by that particular method call   To clarify further  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  When you create the mocked List  Mockito will use the definition of List class to creates its mock     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     If you really want to do this  then have Mockito throw a new RuntimeException   or even better throw a new ArrayIndexOutOfBoundsException   since the API specifies that that is the only valid Exception to be thrown

User · Answer

Note that in general  Mockito does allow throwing checked exceptions so long as the exception is declared in the message signature  For instance  given  class BarException extends Exception        this is a checked exception    interface Foo     Bar frob   throws BarException     it s legal to write   Foo foo   mock Foo class   when foo frob    thenThrow BarException class    However  if you throw a checked exception not declared in the method signature  e g   class QuxException extends Exception        a different checked exception    Foo foo   mock Foo class   when foo frob    thenThrow QuxException class    Mockito will fail at runtime with the somewhat misleading  generic message   Checked exception is invalid for this method  Invalid  QuxException   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

User · Answer

There is the solution with Kotlin    given myObject myCall    willAnswer       throw IOException  Ooops       Where given comes from      import org mockito BDDMockito given

User · Answer

A workaround is to use a willAnswer   method    For example the following works  and doesn t throw a MockitoException but actually throws a checked Exception as required here  using BDDMockito    given someObj someMethod stringArg1   willAnswer  invocation - gt    throw new Exception  abc msg          The equivalent for plain Mockito would to use the doAnswer method

User · Answer

This works for me in Kotlin  when list get 0   thenThrow new ArrayIndexOutOfBoundsException      Note   Throw any defined exception other than Exception

[java] throw checked Exceptions from mocks with Mockito

Examples related to java

Examples related to mocking

Examples related to mockito