app/models/invitation.rb

@@ -6,6 +6,9 @@ class Invitation < ApplicationRecord
 
   before_create :generate_token
 
+  scope :unused, -> { where(used_at: nil) }
+  scope :used, -> { where.not(used_at: nil) }
+
   private
 
   def generate_token

spec/models/invitation_spec.rb

@@ -19,4 +19,26 @@ RSpec.describe Invitation, type: :model do
       expect(token).not_to eq(invitation_2.token)
     end
   end
+
+  describe "scopes" do
+    before do
+      @unused_invitation = create :invitation, user: user
+      @used_invitation   = create :invitation, user: user, used_at: DateTime.now
+      @used_invitation_2 = create :invitation, user: user, used_at: DateTime.now
+    end
+
+    describe "#unused" do
+      it "returns unused invitations" do
+        expect(Invitation.unused.count).to eq(1)
+        expect(Invitation.unused.first).to eq(@unused_invitation)
+      end
+    end
+
+    describe "#used" do
+      it "returns used invitations" do
+        expect(Invitation.used.count).to eq(2)
+        expect(Invitation.used.first).to eq(@used_invitation)
+      end
+    end
+  end
 end