The present application describes a method and system for testing the compliance of a PCIE expansion system to verify that data signals transmitted through multiple data lanes in the expansion system comply with the PCIE requirements. The method for testing a PCIE expansion system comprises delivering the data signals from the data lanes to a compliance board that is configured to loop back at least a first portion of the data signals and transmit a complementary second portion of the data signals to a testing device, and testing a compliance of the second portion of the data signals with the PCIE requirements. The first portion of the data signals is then tested through a second compliance board that is configured to loop back the second portion of the data signals and transmit the first portion of the data signals to the testing device.