Add previews for all customized Devise emails

spec/mailers/previews/devise_mailer_preview.rb

 class DeviseMailerPreview < ActionMailer::Preview
   def confirmation_instructions_for_signup
-    user = User.new(name: 'Jane Doe', email: 'signup@example.com')
-    DeviseMailer.confirmation_instructions(user, 'faketoken', {})
+    DeviseMailer.confirmation_instructions(unsaved_user, 'faketoken', {})
   end
 
   def confirmation_instructions_for_new_email
     user = User.last
+    user.unconfirmed_email = 'unconfirmed@example.com'
+
     DeviseMailer.confirmation_instructions(user, 'faketoken', {})
   end
+
+  def reset_password_instructions
+    DeviseMailer.reset_password_instructions(unsaved_user, 'faketoken', {})
+  end
+
+  def unlock_instructions
+    DeviseMailer.unlock_instructions(unsaved_user, 'faketoken', {})
+  end
+
+  def password_change
+    DeviseMailer.password_change(unsaved_user, {})
+  end
+
+  private
+
+  def unsaved_user
+    User.new(name: 'Jane Doe', email: 'jdoe@example.com')
+  end
 end