1. A computer-assisted method of test assembly for assembling a test comprised of a plurality of slots to be filled by test items, the method comprising: providing a plurality of item collections, each of the plurality of item collections comprising a plurality of test items; executing a test administration script to associate each of the plurality of slots of the test with one of the plurality of item collections from which an item to fill the slot is to be selected, the one of the plurality of item collections including a plurality of eligible test items that meet the content specifications for that slot of the test, and wherein the test administration script comprises a plurality of instruction sets, one of the instruction sets associated with one of the plurality of slots; obtaining an interim test score based on examinee responses to a portion of the test previously assembled and administered to an examinee; further executing the test administration script to apply, using a computer, an optimization process and randomization factor to select the item to fill the next slot of the test while controlling statistical properties of the test based on the interim score and properties of the items within the item collection associated with each of the plurality of slots; and repeating the steps of obtaining the interim test score and applying the optimization process until the test has been completely assembled and administered to the examinee; wherein execution of the test administration script ensures the test meets a content specification while reducing the computational load required to assemble the test.