Stream X-machines have been used to specify real systems requiring to represent complex data structures. One of the advantages of using stream X-machines to specify a system is that it is possible to produce a test set that, under certain conditions, detects all the faults of an implementation. In this paper we present a formal framework to test temporal behaviors in systems where temporal aspects are critical. Temporal requirements are expressed by means of random variables and affect the duration of actions. Implementation relations are presented as well as a method to determine the conformance of an implementation with respect to a specification by applying a test set.