During the manufacturing of centrifugal compressorsCentrifugal compressor, numerous in-process examinations, inspectionsInspections, and testing activities are conducted. Among these, the shop performance test and the mechanical running test hold particular importance for customers. The performance test serves as a key indicator of the compressor’s actual thermodynamic efficiency and mechanical behavior, and helps validate the engineering design and analysis. The results from this test are instrumental in defining the head-capacity curve—its shape and limits—marked by surge at low flow rates and stonewall or stall at high flow rates. This chapter outlines the proper approach to scoping, planning, and executing both performance and mechanical running tests within the compressor manufacturer’s facility. It includes a sample calculation demonstrating how to convert data from test at a certified point into predicted performance under specified operating conditions. Additionally, it covers specialized analyses required by certain users for large-scale compressors.