Different e-learning technologies may offer different incentive factors, which influence behavioural intention. Moreover, when adopting a new e-learning technology for an extended period, learners' perceptions and learning behaviour may change during the learning period. Unfortunately, as formative assessments (FAs) are often continuously performed during a semester, few studies have investigated how the two FA tools: computer-based assessment (CBA) and game-based assessment (GBA), influence learning perception, behavioural intention, and learning achievement during the learning period under the possible existence of the above phenomena. This study used a quasi-experiment design in which one class used CBA as an FA tool and the other used GBA (i.e. Kahoot!) in a university level course for one semester. This study makes the following findings. First, the incentive factors influencing behavioural intention for CBA and for GBA (Kahoot!) differ in the early stage (before the mid-term). Second, the incentive factors influencing behavioural intention fluctuated in both classes over the one-semester experiment. Third, although the CBA class had significantly higher scores than the Kahoot! class for every FA, there was no significant difference between the mid-term and the final term scores (learning achievement) of the two classes.