test: add 50 tests for untested functions; fix nil crash in save-debug-data

Add 11 new test files covering wttrin--save-debug-data,
wttrin--buffer-cache-refresh, wttrin--mode-line-stop,
wttrin--mode-line-start, wttrin-query, wttrin-requery-force,
wttrin-mode-line-click, wttrin-mode-line-force-refresh,
wttrin-fetch-raw-string, wttrin-clear-cache, and wttrin-requery.

Fix bug in wttrin--save-debug-data where nil raw-string caused
(insert nil) crash — reachable when debug mode is on and fetch fails.

Refactor wttrin-requery: extract wttrin--requery-location so the
core kill-buffer-and-query logic is testable without mocking
completing-read.

267 tests total (was 217), all passing.

1 files changed, 69 insertions, 0 deletions

diff --git a/tests/test-wttrin-mode-line-click.el b/tests/test-wttrin-mode-line-click.el
new file mode 100644
index 0000000..fccd45e
--- /dev/null
+++ b/tests/test-wttrin-mode-line-click.el
@@ -0,0 +1,69 @@
+;;; test-wttrin-mode-line-click.el --- Tests for wttrin-mode-line-click -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2025 Craig Jennings
+
+;;; Commentary:
+
+;; Unit tests for wttrin-mode-line-click function.
+;; Tests the left-click handler for the mode-line weather widget.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin)
+(require 'testutil-wttrin)
+
+;;; Setup and Teardown
+
+(defun test-wttrin-mode-line-click-setup ()
+  "Setup for mode-line-click tests."
+  (testutil-wttrin-setup))
+
+(defun test-wttrin-mode-line-click-teardown ()
+  "Teardown for mode-line-click tests."
+  (testutil-wttrin-teardown)
+  (when (get-buffer "*wttr.in*")
+    (kill-buffer "*wttr.in*")))
+
+;;; Normal Cases
+
+(ert-deftest test-wttrin-mode-line-click-normal-opens-weather-for-favorite ()
+  "Clicking the mode-line widget should open weather for the favorite location."
+  (test-wttrin-mode-line-click-setup)
+  (unwind-protect
+      (let ((wttrin-favorite-location "New Orleans, LA")
+            (opened-location nil))
+        (cl-letf (((symbol-function 'wttrin)
+                   (lambda (location) (setq opened-location location))))
+          (wttrin-mode-line-click)
+          (should (equal opened-location "New Orleans, LA"))))
+    (test-wttrin-mode-line-click-teardown)))
+
+(ert-deftest test-wttrin-mode-line-click-normal-passes-exact-location-string ()
+  "The exact favorite location string should be passed to wttrin, not modified."
+  (test-wttrin-mode-line-click-setup)
+  (unwind-protect
+      (let ((wttrin-favorite-location "São Paulo, BR")
+            (opened-location nil))
+        (cl-letf (((symbol-function 'wttrin)
+                   (lambda (location) (setq opened-location location))))
+          (wttrin-mode-line-click)
+          (should (equal opened-location "São Paulo, BR"))))
+    (test-wttrin-mode-line-click-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-wttrin-mode-line-click-boundary-nil-location-is-noop ()
+  "When no favorite location is configured, clicking should do nothing."
+  (test-wttrin-mode-line-click-setup)
+  (unwind-protect
+      (let ((wttrin-favorite-location nil)
+            (wttrin-called nil))
+        (cl-letf (((symbol-function 'wttrin)
+                   (lambda (_location) (setq wttrin-called t))))
+          (wttrin-mode-line-click)
+          (should-not wttrin-called)))
+    (test-wttrin-mode-line-click-teardown)))
+
+(provide 'test-wttrin-mode-line-click)
+;;; test-wttrin-mode-line-click.el ends here