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+;;; test-wttrin-geolocation--parse-ipapi.el --- Tests for ipapi.co response parser -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2026 Craig Jennings
+
+;;; Commentary:
+;; Unit tests for `wttrin-geolocation--parse-ipapi'.  Pure function — no
+;; network, no async.  Covers normal, boundary, and error cases per the
+;; Normal/Boundary/Error discipline.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin-geolocation)
+
+;;; Setup and Teardown
+
+(defun test-wttrin-geolocation--parse-ipapi-setup ()
+  "Setup for ipapi parser tests."
+  nil)
+
+(defun test-wttrin-geolocation--parse-ipapi-teardown ()
+  "Teardown for ipapi parser tests."
+  nil)
+
+;;; Normal Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-normal-full-response-returns-formatted-string ()
+  "A full ipapi.co response yields \"City, Region\"."
+  (let ((json "{\"ip\":\"1.2.3.4\",\"city\":\"Berkeley\",\"region\":\"California\",\"country_name\":\"United States\",\"latitude\":37.87,\"longitude\":-122.27}"))
+    (should (string= "Berkeley, California"
+                     (wttrin-geolocation--parse-ipapi json)))))
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-normal-unicode-preserved ()
+  "Unicode city and region names round-trip through the parser."
+  (let ((json "{\"city\":\"São Paulo\",\"region\":\"São Paulo\"}"))
+    (should (string= "São Paulo, São Paulo"
+                     (wttrin-geolocation--parse-ipapi json)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-boundary-extra-fields-ignored ()
+  "Unknown fields in the response do not affect the parsed result."
+  (let ((json "{\"city\":\"Paris\",\"region\":\"Ile-de-France\",\"currency\":\"EUR\",\"asn\":\"AS1234\"}"))
+    (should (string= "Paris, Ile-de-France"
+                     (wttrin-geolocation--parse-ipapi json)))))
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-boundary-multi-word-city-preserved ()
+  "Multi-word city names are preserved verbatim."
+  (let ((json "{\"city\":\"New Orleans\",\"region\":\"Louisiana\"}"))
+    (should (string= "New Orleans, Louisiana"
+                     (wttrin-geolocation--parse-ipapi json)))))
+
+;;; Error Cases
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-error-nil-input-returns-nil ()
+  "A nil input string returns nil."
+  (should-not (wttrin-geolocation--parse-ipapi nil)))
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-error-empty-string-returns-nil ()
+  "An empty input string returns nil."
+  (should-not (wttrin-geolocation--parse-ipapi "")))
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-error-malformed-json-returns-nil ()
+  "Malformed JSON returns nil rather than signalling."
+  (should-not (wttrin-geolocation--parse-ipapi "{not valid json")))
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-error-missing-city-returns-nil ()
+  "A response without a city field returns nil."
+  (let ((json "{\"region\":\"California\"}"))
+    (should-not (wttrin-geolocation--parse-ipapi json))))
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-error-missing-region-returns-nil ()
+  "A response without a region field returns nil."
+  (let ((json "{\"city\":\"Berkeley\"}"))
+    (should-not (wttrin-geolocation--parse-ipapi json))))
+
+(ert-deftest test-wttrin-geolocation--parse-ipapi-error-api-error-flag-returns-nil ()
+  "An ipapi rate-limit / error response returns nil even if city/region are absent."
+  (let ((json "{\"error\":true,\"reason\":\"RateLimited\",\"message\":\"wait\"}"))
+    (should-not (wttrin-geolocation--parse-ipapi json))))
+
+(provide 'test-wttrin-geolocation--parse-ipapi)
+;;; test-wttrin-geolocation--parse-ipapi.el ends here