Handle non-Excon errors, in case of unexpected api behaviour

app/services/postcode_service.rb

@@ -14,7 +14,9 @@ class PostcodeService
         location_admin_district: parsed_response["result"]["admin_district"],
       }
     rescue Excon::Error => e
-      Rails.logger.warn("An error occurred with the postcode lookup request: #{e} #{e.response.body}")
+      Rails.logger.warn("Postcode lookup request was not successful: #{e} #{e.response.body}")
+    rescue StandardError => e
+      Rails.logger.error("Unexpected error with postcode lookup request: #{e}")
     end
     result
   end

spec/services/postcode_service_spec.rb

@@ -60,5 +60,21 @@ describe PostcodeService do
         service.lookup("A00 0AA")
       end
     end
+
+    context "when the request returns a success response that causes later errors" do
+      before do
+        Excon.stub({}, { body: '{"result": { "admin_district": "District" } }', status: 200 })
+      end
+
+      it "returns nil" do
+        result = service.lookup("A00 0AA")
+        expect(result).to be_nil
+      end
+
+      it "logs the error at error level" do
+        expect(Rails.logger).to receive(:error).with(match "Unexpected error with postcode lookup request")
+        service.lookup("A00 0AA")
+      end
+    end
   end
 end