Because of the demand for advanced measurement systems in the field of modern photonic integrated circuits, optical frequency domain reflectometry (OFDR) is a robust technique for characterizing design-to-fabrication deviations. In this paper we report an OFDR device where the interferometric part is monolithically integrated along with the device under test. We discuss the advantages in terms of compactness and performance, and the importance of the incorporated dispersion de-embedding mechanism. Experimental validation is carried out by interrogating an arrayed waveguide grating on a silicon nitride platform. The results establish the proposed device as a first step in the quest for a universal test structure for integrated devices.