1. A method of compressing a test vector comprising the steps of: generating the test vector, the test vector having a sequence of elements, at least one element comprising a ‘don't care’ value indicating a ‘don't care’ state; producing a random sequence of elements having a same number of elements as the test vector; sequentially segmenting the test vector into segments of the test vector elements; similarly segmenting the random sequence into segments of the random sequence elements corresponding to the test vector segments; comparing each segment of the test vector to a corresponding segment of the random sequence; and creating a compressed test vector from the comparison.