In 1997, Beizer challenged some of the claims made by the supporters of Cleanroom, in particular the elimination of unit testing. He argued that this was clearly contradicting "known testing theory and common sense" and that it was impossible to find a bug without actually compiling code.

He also points out that Cleanroom is never measured against

He casts doubts on the veracity of some of the studies that have evaluated Cleanroom including Basili and Green's (1994) pointing out several flaws in them.

Beizer raises some important issues which cannot be ignored and teaches us to exercise caution in readily embracing new software engineering techniques which claim to solve major problems.