Spring boot Post Test AssertEquals

I ve got a simple test method, that test POST request

  @Test
public void saveItem() {
    //GIVEN
    List<Item> newItems= (List<Item>) itemTestBuilder
        .list()
        .saved()
        .build();


    //WHEN
    ResponseEntity<Item> response = restTemplate.postForEntity(ItemResourceConstants.PATH, newItems, null);

    //THEN

    assertEquals(HttpStatus.CREATED.value(), response.getStatusCodeValue());
}

and it works, but basically to test it correctlly I should check for more conditions. Problem is that the response type is null and have no idea how to check more assertions with that. Anyone has any idea?