Testing towards first preproduction ITk Pixel detector units

For the upgrade of the LHC to the High-Luminosity LHC, the ATLAS inner detector will be replaced with an all-silicon detector, the Inner Tracker (ITk). The innermost part of the ITk will consist of a pixel detector with five layers that will consist of modules combined into serially powered (SP) chains and loaded on ring and stave shaped low mass carbon-fiber local supports (LLS). During 2024, the ITk Pixel project will be in the preproduction period and multiple loading sites will integrate modules on LLSs. Testing these significantly sized and feature-complete detector units is a major challenge and essential in order to ensure their electrical and thermal performance. This contribution describes the development of a large-scale detector test setup detailing on the general infrastructure, the control and monitoring system as well as the readout system. The testing routines will be summarized in this contribution.