The major concern of the successive groups responsible for developing the Unit Tests for Project Physics has been to make the tests representative of both the content and the style of the course. And as the course has developed through successive editions with slightly changed emphasis, so have the approaches taken by the test groups. This paper outlines the basic guidelines for the development of the Project Physics Unit Tests. It tells of past and current activities of the test groups, and, to the extent possible at this time, describes the kinds of Unit Tests that will become available to teachers of Project Physics. (Members of the Project who have served as the test development group include Stephen Brush, William Shurcliff, F. James Rutherford, Andrew Ahlgren, Ashok Khosla, David Clarke, Dean Casperson, Jay Hauben, Banesh Hoffmann, and the authors.)