Disclosed is a shielded clock tree that has one or more clock signal buffers and clock signal splitters, with clock signal wiring connecting the clock signal buffers to the clock signal splitters. Shielding is adjacent the clock signal wiring, where ground wiring connects the shielding to ground. The shielding comprises shield wires positioned adjacent and parallel to the clock signal wiring. The invention provides switches in the ground wiring, and these switches are connected to, and controlled by, a test controller.