Spec the AddressSerializer before changing it

spec/serializers/api/address_serializer_spec.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Api::AddressSerializer do
+  subject(:serializer) { described_class.new(address) }
+  let(:address) { build(:address) }
+
+  describe "#country_name" do
+    it "provides the country's name" do
+      address.country.name = "Australia"
+      expect(serializer.country_name).to eq "Australia"
+    end
+  end
+
+  describe "#state_name" do
+    it "provides the state's abbreviation" do
+      address.state.abbr = "Vic"
+      expect(serializer.state_name).to eq "Vic"
+    end
+  end
+
+  describe "caching" do
+    it "updates with the record" do
+      expect {
+        address.update!(first_name: "Nick")
+      }.to change {
+        serializer.to_json
+      }
+    end
+
+    it "updates even when database wasn't changed" do
+      expect {
+        address.first_name = "Nick"
+      }.to change {
+        serializer.to_json
+      }
+    end
+  end
+end