A distributed system may have some separate interfaces called ports, which makes it necessary to have a separate tester at each port when testing such a system. This kind of test architecture may introduce several issues known as controllability and observability problems. This paper proposes a new method that utilizes a set of transformation rules to construct an auxiliary digraph from a given specification, and the remaining work of generating minimal test sequences without encountering potential controllability or observability problems can be reduced to find proper tours in the constructed digraph. Furthermore, we will show through simple application that our method has better characteristics than the former methods.