Lower estimate of the length of the complete test in the basis $\{x|y\}$

It is proved that the length of the complete test is no less than $n+1$ ($n\ge 2$) for any circuit realizing the function $x_1\vee x_2\vee \ldots \vee x_n$ in the “ Sheffer stroke” basis with possible constant faults of type “1”. An example of such circuit is constructed so that the length of the complete test is exactly $n+1$.