Implement invitation codes

test/models/invite_code_test.rb

@@ -0,0 +1,25 @@
+require "test_helper"
+
+class InviteCodeTest < ActiveSupport::TestCase
+  test "claim! destroys the invitation token" do
+    code = InviteCode.generate!
+
+    assert_difference "InviteCode.count", -1 do
+      InviteCode.claim! code
+    end
+  end
+
+  test "claim! returns true if valid" do
+    assert InviteCode.claim!(InviteCode.generate!)
+  end
+
+  test "claim! is falsy if invalid" do
+    assert_not InviteCode.claim!("invalid")
+  end
+
+  test "generate! creates a new invitation and returns its token" do
+    assert_difference "InviteCode.count", +1 do
+      assert_instance_of String, InviteCode.generate!
+    end
+  end
+end