Simulate throwing an exception that is package protected

Problem: for one of my unit-tests, I want to simulate throwing an exception (io.netty.handler.timeout.TimeoutException) in combination with Mockito. However, Java won’t allow this because the exception is package-protected.

Right now I have the following bit of code:

doAnswer(invocation -> {
            throw new TimeoutException("test-description");
        }).when(someObject).someMethod();

This bit of code does not compile, but I would like to know if there are any alternatives for simulating throwing this exception.

>Solution :

The class io.netty.handler.timeout.TimeoutException itself is public, but its constructors are package-private. You can mock the exception:

doThrow(TimeoutException.class).when(someObject).someMethod();

or:

doThrow(mock(TimeoutException.class)).when(someObject).someMethod();