How to unit test async code with callbacks
 @Test public void deleteEmployee() throws Exception {     EmployeeReqCtx reqCtx = rf.employeeReqCtx();     final boolean[] onSuccess = {false};     reqCtx.delete(10L).fire(new Receiver<Void>() {            @Override            public void onSuccess(Void response) {                  onSuccess[0] = true;            }            @Override            public void onFailure(ServerFailure failure) {                  System.err.println("failure.getMessage() = " + failure.getMessage());             }      });       assertTrue(onSuccess[0]); }  The trick is to use a  final boolean array  because you need to use  values  (finals) within callbacks ...