Currently, 50 + learning systems supporting student question-generation (SQG) activities have been developed. While generating questions of different types is supported in many of these systems, systems allowing students to generate questions around a scenario (i.e. student testlet-generation, STG) are not yet available. Noting the increasing prevalence of testlets in contemporary testing and their learning potential through the lens of anchored instruction, this study aimed to develop a versatile, scaffolded online STG learning system. The results from three evaluative studies supported the learning potential of the world's first-ever STG system and the usefulness of its distinctive functionalities. Specifically, significantly more participants regarded the online STG task as promoting better learning, with the most prominent feature of STG -- the scenario highlighted for the pronounced learning benefits. Additionally, given that the distinct affordances associated with STG based on given text and graphics were well-noted, the practicality of the 'multi-presentation' design concept for scenarios was verified. Furthermore, data from the participants' perceived usefulness of editable and self-created scenarios validated the importance of the 'editability' and 'self-expression' design concepts. Finally, with the distinctive functionalities incorporated in the developed STG system having their respective supporters, the concept of building a diversified STG learning space is upheld.