code:     private void login(String clientId) throws Exception {
          getMockMvc().perform(post("/oauth/token")
                  .accept(MediaType.APPLICATION_JSON_VALUE)
                  .header("Authorization", "Basic " + new String(Base64.encode((clientId + ":" + SECRET).getBytes())))
                  .param("grant_type", "client_credentials")
          )
                  .andExpect(status().isOk())
                  .andReturn().getResponse().getContentAsString();
      }
  
      @Test
  