Testing 1-2-3 is a general purpose testing system developed at the Computer-Based Education Research Laboratory at the University of Illinois for use on NovaNET computer-based education systems. The testing system can be used for: short, teacher-made quizzes, individualized examinations, computer managed instruction curriculum testing, standardized tests, certification tests, and practice examinations. This system currently supports four test item types: multiple choice, multiple selection, short answer, and numeric. Options for result reporting include overall pass/fail scores, individual criteria for up to 26 subscores, and storage and viewing of a student's complete test history. Testing 1-2-3 is structured around several lists of component parts in a single file. Each test is created by specifying which parts will be combined to create a particular test. This guide discusses the following topics: (1) getting started; (2) creating test items; (3) the text mode; (4) the graphics mode; (5) the locate mode; (6) editing displays; (7) shared graphic resources; (8) making section pages; (9) gathering items into tests; (10) customizing tests; (11) testing under the SYS 4 Management System; and (12) assigning tests to students. Sample computer visual displays are illustrated in 22 figures. (SLD)