The paper presents a new method for designing efficient TSC checkers for m-out-of n codes. The method is based on the partitioning of the input code variables into an arbitrary number of r classes. The paper establishes the necessary design conditions that must hold among m, n and r. The checker is basically composed of an m/n to l/z subchecker concatenated with an l/z to 1/2 subchecker. A cost analysis performed reveals that the most economical checkers are obtained for values of r equal to 3, or 4 for the majority of m/n codes with n ≤ 4m. Comparison with earlier designs reveals impressive improvement both in logic complexity and testing complexity.