Identifying and considering test-taking effort is of utmost importance for drawing valid inferences on examinee competency in low-stakes tests. Different approaches exist for doing so. The speed-accuracy+engagement model aims at identifying non-effortful test-taking behavior in terms of nonresponse and rapid guessing based on responses and response times. The model allows for identifying rapid-guessing behavior on the item-by-examinee level whilst jointly modeling the processes underlying rapid guessing and effortful responding. To assess whether the model indeed provides a valid measure of test-taking effort, we investigate: (1) convergent validity with previously developed behavioral as well as self-report measures on guessing behavior and effort; (2) fit within the nomological network of test-taking motivation derived from expectancy-value theory; and (3) ability to detect differences between groups that can be assumed to differ in test-taking effort. Results suggest that the model captures central aspects of non-effortful test-taking behavior. While it does not cover the whole spectrum of non-effortful test-taking behavior, it provides a measure for some aspects of it, in a manner that is less subjective than self-reports. The article concludes with a discussion of implications for the development of behavioral measures of non-effortful test-taking behavior.