At my university, in a Computer Systems course I'm TAing, there are some experiment based assignments in which students are expected to perform experiments, record the results and prepare a report to explain the results.
Post Assignment submission, there's a viva. They're expected to demo the experiments on the same laptops/PCs they did the assignment on.
During the viva, many students are able to reproduce results close to the ones they reported in the assignment submission, while for others there are large deviations.
Slight deviations are okay (and even expected), but large ones are not. Does this constitute cheating?
Demo testing is not running a single instance.
Students are expected to report average, standard deviation
taken over a very large number of instances of the experiment.
On all machines where the TAs have performed the experiments, we have been able to reproduce the results with slight deviations later.
That's why I said slight deviations are okay, but
Large deviations from the reported results might mean they've not honestly reported their own results, but instead mentioned copied, slightly-modified results taken from their friends' assignments.