A testing circuit for testing a series of at least three alternating transmitter and receiver links. The testing circuit including a built-in-self-test (BIST.) macro for generating test data and transmitting the test data to a first link of the series of transmitter and receiver links, and for receiving processed test data from a last link of the series of transmitter receiver links; and at least one test transmission line for transmitting test data received by a link of the series of transmitter and receiver links to a next link of the series of transmitter and receiver links, wherein the at least one test transmission line connects the at least three transmitter and receiver links. A method for testing a series of links having at least three alternating transmitter and receiver links of a plurality of transmitter and receiver links in a SerDes core including generating at least one test data signal; transmitting the at least one test data signal sequentially through the transmitter and receiver links of the series of links; receiving the at least one test data signal from a last link of the series of transmitter and receiver links; and checking the at least one test data signal received.