code: public boolean isVoid() {
          final MockCreationSettings mockSettings = MockUtil.getMockHandler(invocation.getMock())
              .getMockSettings();
          Class<?> returnType = GenericMetadataSupport.inferFrom(mockSettings.getTypeToMock())
              .resolveGenericReturnType(this.method)
              .rawType();
          return returnType == Void.TYPE || returnType == Void.class;
      }
docs: Returns {@code true} is the return type is {@link Void} or represents the pseudo-type to the keyword {@code void}.
  E.g:  {@code void foo()} or {@code Void bar()}