I think that quantitative data collection is appropriate. You could do a Likert scale survey of student perceptions, with questions designed to produce answers about constructivim. You could do a pre-test and post-test methodology (with quantified results) to see of an constructivist instructional design produces changes. 

I like studies that use quantitative instruments, matched with qualitative data collection.  The former is generalizable (if done properly) and the latter provides insights into the actual experiences of the students.

Constructive research is perhaps the most common computer science research method. This type of approach demands a form of validation that doesn't need to be quite as empirically based as in other types of research like exploratory research. The conclusions have to be objectively argued and defined. Here objective arguments must validated by quantitative instruments. As per our research, we can prepare the questionnaire and validated through Likert style method.