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-clear-cache.el b/tests/test-wttrin-clear-cache.el
new file mode 100644
index 0000000..3404cf8
--- /dev/null
+++ b/tests/test-wttrin-clear-cache.el
@@ -0,0 +1,69 @@
+;;; test-wttrin-clear-cache.el --- Tests for wttrin-clear-cache -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2025 Craig Jennings
+
+;;; Commentary:
+
+;; Unit tests for wttrin-clear-cache function.
+;; Tests the interactive command that clears all cached weather data.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin)
+(require 'testutil-wttrin)
+
+;;; Setup and Teardown
+
+(defun test-wttrin-clear-cache-setup ()
+  "Setup for clear-cache tests."
+  (testutil-wttrin-setup))
+
+(defun test-wttrin-clear-cache-teardown ()
+  "Teardown for clear-cache tests."
+  (testutil-wttrin-teardown))
+
+;;; Normal Cases
+
+(ert-deftest test-wttrin-clear-cache-normal-empties-all-entries ()
+  "Clearing the cache should remove all stored weather entries."
+  (test-wttrin-clear-cache-setup)
+  (unwind-protect
+      (progn
+        ;; Populate cache with several entries
+        (testutil-wttrin-add-to-cache "Paris" "data1")
+        (testutil-wttrin-add-to-cache "London" "data2")
+        (testutil-wttrin-add-to-cache "Tokyo" "data3")
+        (should (= 3 (testutil-wttrin-cache-size)))
+        (wttrin-clear-cache)
+        (should (= 0 (testutil-wttrin-cache-size))))
+    (test-wttrin-clear-cache-teardown)))
+
+(ert-deftest test-wttrin-clear-cache-normal-shows-confirmation ()
+  "User should be told the cache was cleared."
+  (test-wttrin-clear-cache-setup)
+  (unwind-protect
+      (let ((displayed-message nil))
+        (cl-letf (((symbol-function 'message)
+                   (lambda (fmt &rest args)
+                     (setq displayed-message (apply #'format fmt args)))))
+          (wttrin-clear-cache)
+          (should displayed-message)
+          (should (string-match-p "cache cleared" displayed-message))))
+    (test-wttrin-clear-cache-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-wttrin-clear-cache-boundary-already-empty ()
+  "Clearing an already empty cache should not error."
+  (test-wttrin-clear-cache-setup)
+  (unwind-protect
+      (progn
+        (should (= 0 (testutil-wttrin-cache-size)))
+        ;; Should not error
+        (wttrin-clear-cache)
+        (should (= 0 (testutil-wttrin-cache-size))))
+    (test-wttrin-clear-cache-teardown)))
+
+(provide 'test-wttrin-clear-cache)
+;;; test-wttrin-clear-cache.el ends here