This paper addresses the issue of remote testing and diagnosis of distributed objects and their services by introducing the concept of a Testable Environment of Distributed Objects (TEDO). A project is currently underway which involves development of TEDO based on fault-tolerant extensions of the Common Object Request Broker Architecture (CORBA). A major part of this effort is a development of test suite supporting remote object connectivity and dynamic testbed configuration. Of particular importance are the increased performance costs incurred by the extended object functionality, as well as interoperability issues arising from heterogeneity of programming environments and their related commercial tools.