add controller tests

spec/factories/invite.rb

@@ -0,0 +1,15 @@
+require 'factory_bot'
+
+FactoryBot.define do
+  factory :invite do
+    user { create :user }
+    group { create :group }
+    email { Faker::Internet.email }
+
+    factory :expired_invite do
+      after :create do |invite|
+        invite.update_column(:expires_at, Time.now.yesterday)
+      end
+    end
+  end
+end