In any control chart in PROC SHEWHART, when there are only 2 points on the chart or in a phase and both points are in Zone A or beyond, the TESTS=5 option fails to signal the pattern. Similarly, when there are only 4 points on the chart or in a phase and all 4 points are in Zone B or beyond, the TESTS=6 option fails to signal the pattern.

There is no circumvention for this problem.