Spring FragmentsRendering, add getViews or similar to facilitate Unit Tests

When writing Unit-Tests for my controllers, I noticed that the modelAndViews list of FragmentsRendering is not accessible anywhere, effectively preventing me from write Tests that ensure the right views have been added to the FragmentRendering. Furthermore, the way the Builder is invoked prevents effective mocking of the FragmentsRenderingBuilder. Leaving only reflection to access the content. There should be a better way:

FragmentsRendering fragments = adminController.deleteUser(authenticationMock, "mockid", httpServletRequestMock);
// asssertThat(fragments .getViews()).hasSize(2); // This does not work