According to Control-Mastery Theory (CMT)—a cognitive-dynamic relational theory of mental functioning, psychopathology, and psychotherapy—patients come to therapy with an unconscious plan to disprove their pathogenic beliefs and achieve adaptive goals. One of the primary ways patients work to disconfirm their pathogenic beliefs is by testing them within the therapeutic relationship. The present study aimed to replicate and expand the results of previous studies suggesting that therapists’ responses that disconfirmed patient’s pathogenic beliefs were predictive of patients’ within-session progress. Moreover, we wanted to investigate whether these interventions correlated with the therapeutic alliance. Transcriptions of 81 sessions from five brief psychodynamic psychotherapies were assessed by 11 independent raters. For each case, the patient’s plan was formulated and tests identified, the accuracy of the therapist’s responses to these tests was rated, and the impact of the therapist’s interventions on the patient’s subsequent communications and their relationship with the therapeutic alliance was measured. The results supported the central hypothesis of the CMT that when the therapist’s interventions passed the patient’s tests, the patient showed signs of improvement. Moreover, the ability of the therapist to pass the patient’s tests correlated with the therapeutic alliance. The clinical implications and the limitations of these findings are discussed, together with the relevance of a good case formulation for clinicians’ optimal responsiveness.