A portable, automated telephone line test device includes a test module which applies test signals to a telephone line to be tested and detects electrical characteristics of the telephone line, and a user interface module. The user interface module includes a microprocessor, a display, a keyboard and a program memory in accordance with a standard microcomputer architecture. The processor of the user interface module is programmed to control the test module to perform a pre-programmed sequence of tests. The display provides indications of the tests being performed. The programmed sequence is varied by the device according to test results. Depending on the results obtained, the device also provides interpretative diagnostic messages and instructs the user to carry out additional test procedures.