Non-destructive testing is a group of methods which are widespread and desirable for a very long time because they are based on a fact that they don't leave any effects or consequences on testing materials, thus don't generate unnecessary expenses in making and testing products. Beginnings of such testing in industry date back to mid-19th century when there was a necessity to test parts in industry whose failure represents grave danger for people and their lives, for machine parts and machines, as well as significant financial loss. Crucial discoveries in physics during 19th and mid-20th century made conditions for development of mentioned methods and their profiling which have become irreplaceable in all forms of activities in mechanical engineering, as well as in electrical and civil engineering, medicine, aeronautics, petroleum engineering and transport. With further technological developments, as well as developments in automatization, robotics, and in the past few decades computerization, these methods experience constant improvement to this day. In this paper emphasis is placed on the three most widespread non-destructive testing methods; magnetic particle testing, liquid penetrant testing and ultrasonic testing. Here is described the way in which mentioned methods are used, physical principles behind them, equipment in use with these methods and their practical application on the example of testing and quality control in the technological process of plain bearing reparation.