Don't confuse the properties you'd like the tests to have with the properties they do have, or with the properties they need in order to serve their purpose effectively. No effort is put into getting IQ tests to resist practice effects or knowledge of the structure of the questions, because taking the tests is not common.

Mountains of effort go into the same project for standardized tests, because taking those tests is common, and the whole point is to evaluate people for what they are rather than what they would like you to think they are.