An aspect of the present invention facilitates testing of client systems consuming contractual services on different server systems. In one embodiment, a contract (for which the client system is sought to be tested) is first inspected to determine the set of contractual services present in the contract and a minimal implementation for each of the determined set of contractual services is generated. The minimal implementations are designed to merely provide arbitrary outputs consistent with the contract. On receiving a request to invoke a desired one of the set of contractual services from the client system, a corresponding response is sent due to invocation of the (minimal) implementation generated for the desired contractual service, thereby facilitating testing of client system for a different server system.