RuntimeService runtimeService = activitiRule.getRuntimeService();
TaskService taskService = activitiRule.getTaskService();
HistoryService historyService = activitiRule.getHistoryService();
// Prepare mock for muleService
MuleService muleService = mock(MuleService.class);
Mocks.register("mule", muleService);
// Start process instance
ProcessInstance processInstance = runtimeService.startProcessInstanceByKey("open-account-mule");