Psychotherapists can experience various kinds of emotions in response to their patients’ communications and behaviors over the course of therapy. These may be understood in the context of interpersonal dynamics associated with patients’ testing activity. The concept of testing, as part of the patient’s plan for therapy, is explained from the perspective of Control-Mastery Theory. Diferent kinds of testing behaviors, aimed at disconfrming the patient’s pathogenic beliefs, may evoke diferent emotions in the therapist. Understanding the patient’s testing strategies can help to make sense of the therapist’s emotional reactions, manage countertransference, and guide therapeutic responses. This paper describes testing behaviors, according to the patient’s compliance and non-compliance with pathogenic beliefs, along with corresponding therapist emotional responses. A descriptive clinical case is provided to illustrate various tests and their associated emotional reactions within a therapy session.