Hi [firstName] –
Thank you so much for meeting with me [& someone] last week. Your feedback is incredibly helpful for our team; it helps us know how to build the best app we can for volunteers!
For example, from your test session, we learned that [1–2 key insights from their test].
[Could you please send us [someone's contact info]? We'd love to reach out!]
Thanks again for all your help – we'll keep you posted of future testing opportunities. Be sure to track your hour helping us test on Unself !
Have a great rest of your week,
– Elizabeth