Yes, when you run a test and have testers complete your test process, they become part of your core 'community'.
After each test, you can retarget testers in various ways, including:
Targeting your entire community
Targeting testers by past tests
Targeting testers via Tags
Targeting specific testers you choose
You can select your option from the Participants tab when you are designing your test.
Any testers that match your selection will receive an email invite to join your test. There is no guarantee that all testers will participate again, but we usually see 60-80% follow-up participation when testers are retargeted.