The size and complexity of software products have expanded significantly, prompting researchers to focus on quality assessment by quantitatively assessing software product’s reliability growth. Several time dependent software reliability growth models (SRGMs) have been produced and are available in this regard. The authors evaluated errors of varied severity, but they believed that low severity faults would be repaired first, followed by high severity faults. Furthermore, the authors assumed in the change point model that the team changed their strategy, i.e., the fault detection rate changed after a particular time but making a plan and executing that strategy takes a long time, and as a result, the industry confronts a delay in software launching. As a result, two fault categories (low and high severity) are considered in this study, and two types of testing effort function (TEF) related to fault detection rate are presented to detect and fix them. Because parameters have such a large impact on model performance, their sensitivity is also investigated.