We investigated the effects of computerized adaptive testing (CAT) versus computerized fixed item testing (FIT) of reasoning ability on current motivation in terms of situational fear of failure and subjective probability of success, as well as flow. A group of 174 students (aged 15-21) from two German secondary schools was presented either a CAT or a FIT version of a matrices test; motivational variables were assessed during a short break in testing. More situational fear of failure and less subjective probability of success were reported using CAT compared to FIT. Self-reported flow did not differ between test mode conditions. When we addressed the hypothesis that adaptive testing is equally motivating for both high and lower performers, test performance appeared to moderate the relationship of test mode and subjective probability of success: Only during FIT was subjective probability of success higher with lower test performance. This moderation effect was also revealed for the relationship of test mode and flow. However, as average reported motivation was lower during CAT, results contradict assumptions of enhanced motivation during CAT. Results are discussed in relation to self-concept relevance of testing domains and with reference to test fairness.