  @Test
  public void readRssi_disconnected() {

    readRssiTestObserver = corePeripheral.readRssi().test();

    readRssiTestObserver.assertError(
        throwable -> {
          PeripheralError error = (PeripheralError) throwable;
          return error != null && error.getCode() == DISCONNECTED;
        });
  }