Strength evaluation of building components by analysis and in-place load testing is recommended in cases where the degree of suspected deficiencies in design, materials or construction cannot be readily determined. In the study, the purpose of the tests was to evaluate the performance of prestressed concrete hollow core slab (HCS) units carrying dead and live loads as composite members with topping concrete. The first test was conducted on HCS-300 panels, some of which were already installed in the buildings. A monotonic loading test on the ground at the construction site was performed on a non-composite panel to evaluate the actual composite panel's performance. In accordance with the project's quality procedures, to verify the performance of the HCS-400 panels, the second test was decided to be performed on HCS-400 composite panels in the precast plant prior to starting the mass production. The paper describes the application of monotonic loading test procedures and acceptance of test results according to the American ACI 318 standard.