From what I remember, it was a comprehensive evaluation of the different models, with all the available means that the Dutch air force could have.
Obviously, at that time it was not possible to make an in-flight evaluation of the F-35, so the evaluation was made from the paper information provided by the manufacturer to the Dutch air force, whereas the Dutch air force went on the spot to where the other aircraft were manufactured and performed an in-flight evaluation of those aircraft. That in-flight evaluation was a pretty comprehensive one. It involved several flights addressing several types of operational concerns. They made their evaluation and they came back with their conclusions, and the result of that evaluation was published in the Dutch press.