An apparatus such as a tool for testing lines at a network distribution cabinet allows the connection to the network of subscriber twisted pairs. The apparatus includes inputs for the connection of probes adapted to contact pairs of connection terminals of the distribution cabinet for the connection of the subscriber twisted pairs; a line test unit adapted to perform tests on the lines under the control of a programmable control unit; at least one memory for storing the results of the tests. The control unit is adapted to automatically perform a test of the lines terminating at the distribution cabinet according to a predetermined sequence, and to store the results of the test in a structured form in which a unique association is established between a physical position of each pair of terminal clamps in the distribution cabinet and the results of the test conducted on the corresponding lines.