Most of the recent literature investigates mathematical analyses performed on the simulated behavior of the delay physically unclonable function (PUF). These analyses are not sufficient to characterize the PUF leakage under actual operating conditions, and it is hard to model the distribution of the noise that might confuse the assessment of the PUF. Furthermore, simulated analyses may lead to an overestimation of the risk. We show that the availability of an embedded image of the target PUF is important for assessing security against real attacks by considering different input conditions. In this paper, we propose a delay PUF assessment method that combines side-channel analyses and modeling analyses. Our proposed method is the last piece of the all-in-one methodology to assess the security of the delay PUF. Finally, we conduct an experiment to evaluate a real arbiter-PUF (APUF) with our proposed assessment method. Our result shows that a modeling analysis using random forest (RF) and advanced support vector machine (SVM) are suitable for the APUF in the assessment method.