Many observers harbor misgivings about their telescope.
Sure, there are ways to check the accuracy of individual components but for many they are hard to understand or require costly reference optics and other test equipment. Besides, telescope users are interested in the performance of the entire optical train, not just the main optical element. What is really needed is a test that can be used at the observing site, so that all the problems that impact on a telescope's performance can be diagnosed. Yes, the star test is such a method. It uses the entire working telescope.