All Ruby tests raising: undefined method `authenticate' for nil:NilClass

This question has been answered on Twitter by @MatthewClosson

@jeffehh You need to create a spec/support/devise.rb file as specified here https://github.com/plataformatec/devise#test-helpers to include the devise test helpers #ruby

Thanks once again.

I'm aware you're using Rspec but you can run into this same issue with Test::Unit. You just need to add the devise test helpers to test/test_helper.rb

class ActiveSupport::TestCase
  include Devise::TestHelpers
end

The above answer did not work for me (RSpec 3.1)

See https://stackoverflow.com/a/21166482/1161743 for a solution that worked for me.

You will need to log out an anonymous user before setting up variables:

before :each do
  sign_out :user
end