The ktest utility draws on the database of keyword characteristics to provide a simple declarative language for constructing tests. Each mechanical stage can be run through an exercise of each of its positions. This can include commands that attempt to send the stage into its hardware and software error limits. All of the results are recorded for posterity and intercomparison.
For ESI the test ensemble included some 9000 sub-tests and ran for over six hours. The tests found several instances of unintended friction, collision of parts, and loosening screws. As a result of this testing the partially-assembled instrument was redesigned and fixed. By the time ESI reached Keck most motorized components had been through 5000 position cycles. All exercised stages worked, and ESI began science observations before midnight on its first night.