[java] throw checked Exceptions from mocks with Mockito

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<String> 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?

This works for me in Kotlin:

when(list.get(0)).thenThrow(new ArrayIndexOutOfBoundsException());

Note : Throw any defined exception other than Exception()

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 -> { throw new Exception("abc msg"); });

The equivalent for plain Mockito would to use the doAnswer method

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.

There is the solution with Kotlin :

given(myObject.myCall()).willAnswer {
    throw IOException("Ooops")
}

Where given comes from

import org.mockito.BDDMockito.given