Ozlab has been developed to cater for testing which is in part manual and where test users are not aware that the system they seem to interact with is faked. In this way developers can use their human capacity for interactive communication to find suitable human-computer dialogue structures. The chapter argues that the tool itself allows other groups to become interaction designers, since little expertise in programming is needed, while an understanding of every application area as well as an understanding of the need of every user group is always neede