A testing circuit in an integrated circuit indirectly measures a voltage at a node of other circuitry in the integrated circuit. The testing circuit includes a transistor having a control electrode, a first conducting electrode coupled to a first pad, a second conducting electrode coupled to a terminal of a power supply, and one or more switches for selectively coupling the control electrode to one of the node and a second pad. A method includes determining a relationship between drain current and gate voltage of the transistor when the control electrode is coupled to the second pad. A voltage at the node is determined by relating the current through the first conducting electrode of the transistor when control electrode is coupled to the node.