EligibleInstances returns a list of instances that belong to group that are eligible for termination It does not include any instances that match the list of exceptions.

Fake returns a "fake" terminator that just outputs a message upon instance termination.

PickRandomInstance randomly selects an eligible instance from a group.

Terminate executes the "terminate" command.

UnleashedInTestEnv is an error returned by Terminate if running unleashed in the test environment, which is not allowed.