Yes, you can ask testers to leave an honest review of your product in the app store / play store or other similar platforms, as a part of the test process (e.g. leaving a review in the app store could one of the tasks when you design the test).
We do not require testers to do this in order to receive an incentive, so it should be explicitly stated that this is optional.
💡Want to learn more? Book a call/demo with our team or get in touch through our contact form.