Evaluating interface usability and system functionality is time-consuming and effort-intense. The short time-span involved in development iterations, such as those in agile development, makes it challenging for software teams to perform ongoing interface usability evaluation and system functionality testing. We propose a way to perform product ongoing evaluation, thus enabling software teams to perform interface usability evaluation alongside automated system functionality testing. We use formal task models, created in our defined TaMoGolog task modeling language, to conduct product evaluation experiments through TaMUlator. TaMUlator is a tool we developed for use at the Integrated Development Environment (IDE) level. Our case study revealed that software teams can easily engage in system evaluation by using TaMUlator on an iterative basis. © 2012 ACM.