Collecting process data in computer-based assessments provides opportunities to describe examinee behaviour during a test-taking session. The number of actions taken by students while interacting with an item is in this context a variable that has been gaining attention. The present study aims to investigate how the number of actions performed on constructed-response items relates to self-reported effort, performance, and item cluster position in the test. The theory of planned behaviour was used as an interpretative framework. Data from two item clusters of the 2015 Swedish Programme for International Student Assessment (PISA) Science administration were utilised. Results showed that the number of actions was significantly related to performance on the items, self-reported test-taking effort, and cluster position. Latent variable models were examined separately for performance-level groups. Overall, the number of actions performed on constructed-response items as a behavioural indicator in testing situations may be useful in gauging test-taking engagement.