How to get variable from object which is @RestController, without knowing object name, in integration test

So basically I have some @RestController. I wrote some integration test. Which starts like Map response = testRestTemplate.getForObject which perform connection to my controller and then I check response. But now I also need to check some variables in that controller. And question is that: how can I get this variable if I dont have any link to my controller. I cant write like ReflectionTestUtils.getField(controller, "variableName") coz I dont have controller variable in test.