Dr. William C. Hetzel is an expert in the field of software testing.
He compiled the papers from the 1972 Computer Program Test Methods Symposium, also known as the Chapel Hill Symposium, into the book Program Test Methods.
[1] The book, published in 1973, details the problems of software validation and testing.
[2] Hetzel and Dave Gelperin co-found the Software Quality Engineering consultancy firm in 1986.
In 1988 they classified the phases and goals of software testing into the following stages:[3]