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+;;; test-wttrin-geolocation--parse-ipwhois.el --- Tests for ipwho.is response parser -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2026 Craig Jennings
+
+;;; Commentary:
+;; Unit tests for `wttrin-geolocation--parse-ipwhois'.  Pure function — no
+;; network, no async.  The ipwho.is response carries a `success' flag which
+;; is false on rate-limit / lookup failure even when the response is
+;; well-formed JSON.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin-geolocation)
+
+;;; Setup and Teardown
+
+(defun test-wttrin-geolocation--parse-ipwhois-setup ()
+  "Setup for ipwho.is parser tests."
+  nil)
+
+(defun test-wttrin-geolocation--parse-ipwhois-teardown ()
+  "Teardown for ipwho.is parser tests."
+  nil)
+
+;;; Normal Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipwhois-normal-success-response-returns-formatted-string ()
+  "A successful ipwho.is response yields \"City, Region\"."
+  (let ((json "{\"ip\":\"8.8.8.8\",\"success\":true,\"type\":\"IPv4\",\"country\":\"United States\",\"country_code\":\"US\",\"region\":\"California\",\"region_code\":\"CA\",\"city\":\"Mountain View\",\"latitude\":37.386,\"longitude\":-122.0838}"))
+    (should (string= "Mountain View, California"
+                     (wttrin-geolocation--parse-ipwhois json)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipwhois-boundary-unicode-preserved ()
+  "Unicode city and region names round-trip through the parser."
+  (let ((json "{\"success\":true,\"city\":\"München\",\"region\":\"Bayern\"}"))
+    (should (string= "München, Bayern"
+                     (wttrin-geolocation--parse-ipwhois json)))))
+
+;;; Error Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipwhois-error-nil-input-returns-nil ()
+  "A nil input string returns nil."
+  (should-not (wttrin-geolocation--parse-ipwhois nil)))
+
+(ert-deftest test-wttrin-geolocation--parse-ipwhois-error-success-false-returns-nil ()
+  "A response with `success: false' returns nil even if city/region are present."
+  (let ((json "{\"success\":false,\"message\":\"rate limit reached\",\"city\":\"Anywhere\",\"region\":\"Anywhere\"}"))
+    (should-not (wttrin-geolocation--parse-ipwhois json))))
+
+(ert-deftest test-wttrin-geolocation--parse-ipwhois-error-missing-city-returns-nil ()
+  "A success response without a city field returns nil."
+  (let ((json "{\"success\":true,\"region\":\"California\"}"))
+    (should-not (wttrin-geolocation--parse-ipwhois json))))
+
+(ert-deftest test-wttrin-geolocation--parse-ipwhois-error-malformed-json-returns-nil ()
+  "Malformed JSON returns nil rather than signalling."
+  (should-not (wttrin-geolocation--parse-ipwhois "{\"success\":true,\"city\":")))
+
+(provide 'test-wttrin-geolocation--parse-ipwhois)
+;;; test-wttrin-geolocation--parse-ipwhois.el ends here