Emotion research in the area of software engineering has gained significant attention. Mostly this research has been focused on understanding the role of emotions in software programming carried out within collaborative software development environments. With the purpose of providing more evidence on emotion research in the early stages of the software life cycle, in this paper, we report the results of a live study conducted in competitive conditions. The main objective of the study is to analyze the emotions expressed by competitors when performing verification tasks with the support of CoSTest, a model-driven testing tool. Our results show that participants tend to experience more positive emotions (e.g., attentive, alert, active) than negative emotions (upset, hostile, afraid) when verification tasks are performed in an online contest.