I am new to devise and rails and I just integrated devise with my sample app. What I noticed is after creating a user model, all my unit tests were failing. I went
The failure would have to be happening in the test setup, before the actual test. You are probably trying to set up users with identical email addresses, either via fixtures or factories.
If you are using fixtures, make sure each user is given a different email address. If you are using factories, use a sequence to generate a unique email addresses for each user that's created.