Easily testable logical networks based on a 'widened long flip-flop'
  The article describes an attempt to solve at once three basic problems arising at testing a complex digital equipment for defects: 1) the problem of an exponential increasing of the complexity of testing the equipment with the complexity of the equipment; 2) the problem of testing of the tester; 3) the problem of a mutual masking of defects. The proposed solution is nothing more than using certain limitations for connections between usual logical gates. Arbitrary multiple stuck-at-faults are supposed as defects. 
Nick Stukach