In this monograph, the author focuses on trace and testing semantics for nondeterministic and probabilistic processes represented by simple probabilistic automata. A trace is a sequence of activities labeling a sequence of transitions performed by a process, thus abstracting from branching points in the process behavior. A test is formalized as a nondeterministic and probabilistic process extended with success states or success actions, which is run in parallel with the process under test thus resulting in an interaction or testing system. Written as a comprehensive review of the topic, the...