It is recommended to evaluate the properties using three points bending. The upper side of the sample is submited to compression stress. On the other hand, the lower side of the sample, the thin film is submited to tension stress.
Since, the thickness of the Thin film is relatively “Thin” the stress distribution on the thin film can be considered as uniform (at tension).
Naturally, the bending should be preformed at “low” rate in order to record the exact point of thin film brakeage / dismantle.