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+;;; test-wttrin-geolocation--parse-ipinfo.el --- Tests for ipinfo.io response parser -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2026 Craig Jennings
+
+;;; Commentary:
+;; Unit tests for `wttrin-geolocation--parse-ipinfo'.  Pure function — no
+;; network, no async.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin-geolocation)
+
+;;; Setup and Teardown
+
+(defun test-wttrin-geolocation--parse-ipinfo-setup ()
+  "Setup for ipinfo parser tests."
+  nil)
+
+(defun test-wttrin-geolocation--parse-ipinfo-teardown ()
+  "Teardown for ipinfo parser tests."
+  nil)
+
+;;; Normal Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipinfo-normal-full-response-returns-formatted-string ()
+  "A full ipinfo.io response yields \"City, Region\"."
+  (let ((json "{\"ip\":\"8.8.8.8\",\"city\":\"Mountain View\",\"region\":\"California\",\"country\":\"US\",\"loc\":\"37.3860,-122.0838\",\"org\":\"AS15169 Google LLC\",\"postal\":\"94035\",\"timezone\":\"America/Los_Angeles\"}"))
+    (should (string= "Mountain View, California"
+                     (wttrin-geolocation--parse-ipinfo json)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipinfo-boundary-minimal-fields-works ()
+  "A response with only city and region parses correctly."
+  (let ((json "{\"city\":\"Berlin\",\"region\":\"Berlin\"}"))
+    (should (string= "Berlin, Berlin"
+                     (wttrin-geolocation--parse-ipinfo json)))))
+
+;;; Error Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipinfo-error-nil-input-returns-nil ()
+  "A nil input string returns nil."
+  (should-not (wttrin-geolocation--parse-ipinfo nil)))
+
+(ert-deftest test-wttrin-geolocation--parse-ipinfo-error-malformed-json-returns-nil ()
+  "Malformed JSON returns nil rather than signalling."
+  (should-not (wttrin-geolocation--parse-ipinfo "not json at all")))
+
+(ert-deftest test-wttrin-geolocation--parse-ipinfo-error-missing-city-returns-nil ()
+  "A response without a city field returns nil."
+  (let ((json "{\"region\":\"California\",\"country\":\"US\"}"))
+    (should-not (wttrin-geolocation--parse-ipinfo json))))
+
+(ert-deftest test-wttrin-geolocation--parse-ipinfo-error-missing-region-returns-nil ()
+  "A response without a region field returns nil."
+  (let ((json "{\"city\":\"Mountain View\",\"country\":\"US\"}"))
+    (should-not (wttrin-geolocation--parse-ipinfo json))))
+
+(provide 'test-wttrin-geolocation--parse-ipinfo)
+;;; test-wttrin-geolocation--parse-ipinfo.el ends here