Hi Hardik, sorry for the late response.
The problem is related to the LocalTaskService, which ends up having an entity manager. The escalation is executed (using a new entity manager, the task is reasigned, but when in line 145 you get the task, you get an outdate one (which is in entity manager cache I imagine).
If you add this line before line 145,
localTaskService = new LocalTaskService(taskService);
it will create a new entity manager and the test will run ok!
I know the jbpm team is looking at this issue and probably get a better solution.
Thanks!
Demian