Strange rails behaviour: class methods doesnt work as expected...

Question

In Profile model class

def add_friendship_request(friend_id)
  Friendship.testing2 # doesnt works
  Profile.testing2 # works
end

def self.testing2
  'ss'
end

in my Friendship model class

def self.testing2
  'ss'
end

I got this error:

undefined method `testing2' for #<Class:0x58eea7c>

Fixed: restarted my pc