Although the type of test chosen for a given purpose shapes the implementation, so too do implementation constraints imposed by the organization for which the test is developed or selected restrict the nature of the test that is chosen. Thus, implementation issues must be considered before a test format is chosen and research and development begin to ensure the test fits the organization’s needs and staffing context and reconsidered when the test is complete to ensure the implementation procedures support valid interpretations of test scores. Because many implementation decisions affect other decisions about implementation as well as the choice of test, an iterative process in which decisions are revisited will result in an implementation plan that is aligned with the nature of the test to be given and the conditions under which it is to be given. For example, a decision to create only one form of a test to control development costs may limit the frequency with which retests are offered. Conversely, a requirement to allow retests every 6 months based on union contracts, corporate culture, or past practices may necessitate the development of multiple forms or the selection of test types that are less susceptible to practice effects.