In this paper, we first show that the logistic testing-effort function is practically acceptable/helpful for modeling software reliability growth and providing a reasonable description of resource consumption. Therefore, in addition to the exponential-shaped models, we will integrate the logistic testing-effort function into S-shaped model for further analysis. The model is designated as the Yamada Delayed S-shaped model. A realistic failure data set is used in the experiments to demonstrate the estimation procedures and results. Furthermore, the analysis of the proposed model under imperfect debugging environment is investigated. In fact, from these experimental results and discussions, it is apparent that the logistic testing-effort function is well suitable for making estimations of resource consumption during the software development/testing phase. 2. Software reliability growth modeling and testing-effort function 2.1 SRGM with logistic testing-effort function In this section, we will first review logistic testing-effort functions. During the software-testing phase,