However, both of these methods cannot guarantee that the final CAT will meet all specifications. As an alternative, Van der Linden e Reese (1998) proposed the shadow test approach, a 2-stage procedure for item selection where 0-1 linear
programming techniques are applied to make sure that all specifications will be met. During the first stage, a full-length test is constructed (the shadow test) that performs optimal with respect to the item selection rule at the current ability estimate and meets all the specifications. During the 2nd stage, the best unadministered item is selected from the shadow test to be presented to the candidate. For an extensive description of the shadow test approach, see also Van der Linden (2005, Chap. 9).