without camunda BPM assert

without camunda BPM assert.java

// make sure process instance is started
assertNotNull(runtimeService.createProcessInstanceQuery()
    .processInstanceId(processInstance.getId())
    .singleResult());

// make sure the task with id "approveInvoice" & candidate group "backoffice" exists
Task task = taskService.createTaskQuery()
  .taskCandidateGroup("backoffice")
  .processInstanceId(processInstance.getId())
  .taskDefinitionKey("approveInvoice")
  .singleResult();
assertNotNull(task);

// make sure it is not assigned
assertNull(task.getAssignee());