Following tests present in OrderServiceTest for this method. 
discontinueOrderWithNonCodedReason_shouldPopulateCorrectAttributesOnBothOrders()
discontinueOrderWithConcept_shouldPopulateCorrectAttributesOnBothOrders()
discontinueOrderWithNonCodedReason_shouldFailWhenItIsADiscontinueOrder()
discontinueOrderWithConcept_shouldFailWhenItIsADiscontinueOrder()