It has been a great challenge to reliability engineers to evaluate the reliability of their products within an affordable amount of time and effort. Accelerated tests (ATs) combined with censoring have been effectively used for this purpose. ATs are further classified into accelerated life tests (ALTs) and accelerated degradation tests (ADTs). In the former, failure times of test units are observed while, in the latter, their performance characteristics are measured over time. In this paper, the literature on planning ADTs is reviewed with respect to the test scenario, degradation model assumed, and analysis method employed. The literature on planning DTs without acceleration is also reviewed. Finally, recommendations for future research directions are provided. Significance: ADTs are indispensable for evaluating today's highly reliable products. Reliability engineers can benefit from the present review in selecting the test scenario, degradation model, estimation and optimization methods that are appropriate for evaluating their products through a DT or an ADT.