Missing responsebody with MockMvc in Spring restAPI

Im trying to make a small test to test my Spring rest API. my controller looks like this:

@RestController
@RequestMapping("/tokenservice/v1")

public class TokenController {

  private ConfigService configService = new ConfigService();

  // PassiveExpiringMap takes millisecond parameter, and will automatically remove any entry that has expired when the map is accessed, before returning anything. Is not Synq
  private PassiveExpiringMap<String, SensitiveData> dataStores = new PassiveExpiringMap<String, SensitiveData>(configService.getTTL());

  // wrapper for dataStores. Collections.synchronizedMap is used to make the map thread-safe
  private Map<String, SensitiveData> synqMap = Collections.synchronizedMap(dataStores);

  // Routing to the post method. Receives text/plain and returns a "random" UUID back.  https://example:8443/tokenservice/v1/sensitivedata
  @RequestMapping(value = "/sensitivedata", method = RequestMethod.POST, consumes = "text/plain")
  public String postMethod(@RequestBody String secretThings) {
    String token = UUID.randomUUID().toString();
    SensitiveData sensitiveData = new SensitiveData(token, secretThings);
    synqMap.put(token, sensitiveData);
    return token;
  }

  // Routing to the get method. Gets data that matches UUID token.     https://example:8443/tokenservice/v1/sensitivedata?token=<UUID>
  @GetMapping("/sensitivedata")
  public String getData(@RequestParam("token") String token) {
    if (synqMap.containsKey(token)) {
      return synqMap.get(token).getDataToStore();
    } else {
      return "Token not found or has expired";
    }
  }
}

My test looks like this:

MvcResult result = mvc.perform(post("/tokenservice/v1/sensitivedata")
      .with(user("user1").password("secret1"))
      .contentType("text/plain;charset=UTF-8")
      .content("testdata4"))
      .andReturn();

    String token = result.getResponse().getContentAsString();

I thought i would be able to get the token from the body but when i run the test the responsebody is emtpy.

Can see that it hits the correct method and it posts the body

But the response is empty instead of returning the "token"