How stub instanseof in Mockito in java?

I have method that accept argument of Object type. But inside of method checked if is e.g. List type. Is possible in mockito to stub it? E.g.

public void checkValue(Object arg) {
   if (arg instanceof List) {
    ....

So in mockito:

Object myObject=mock(Object.class);

After I need write something like:

when (myObject instanceof List).thenReturn List

How it can be done? Thanks.

Sure, you can mock how ever you want. Ex:

Object o = mock(List.class);

There is an advice that states

Do not mock types you don't own

So your test should accept an instance of a real list object new ArrayList() instead of a mock.

Should you only mock types you own?