How I test out mailers?

Ruby on Rails
1

I am using devise invitation. Should I test it out because we are placing a limit of invitations to 5 per user. Or since devise has already been tested I should not be testing it again.

Thanks

2

email_spec GitHub - email-spec/email-spec: Collection of RSpec/MiniTest matchers and Cucumber steps for testing email in a ruby app using ActionMailer or Pony has some nice methods for validating emails in test.