Integrated circuits often are provided with BIST (built-in self-test) circuitry. The BIST circuitry may be used to test parts of a circuit during the design of a circuit. For example an integrated circuit which has BIST circuitry can be tested by automated test equipment (ATE). The BIST circuitry may comprise one or more scan chains. The ATE may be arranged to scan in a plurality of scan values and to receive a plurality of output scan values. These output scan values can be analysed to determine if the part of the circuit under test is performing correctly.