Standard and encyclopedic definitions of terms used in testing machines. Generalized into a single theory of experiment its individual sections. Presented modern methods and means of testing parts, assemblies, mechanisms and machines in general. Modern methods of primary and mathematical processing of test results using consent criteria, confidence intervals and means of scientific penetration are considered The feasibility of experimental determination of evaluation of operational efficiency and other properties of firing tractors . has been proved Characteristic examples of methods of processing the results of the study of logging machines in production conditions are given. The training manual is intended for students of forestry and forestry engineering faculties, graduate students, researchers and engineers of the logging industry and forestry . ;Griff:Admitted by the Educational and Methodological Association for Forestry Education as a teaching aid for university students