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, 122 insertions, 0 deletions

diff --git a/tests/test-wttrin-query.el b/tests/test-wttrin-query.el
new file mode 100644
index 0000000..a44040a
--- /dev/null
+++ b/tests/test-wttrin-query.el
@@ -0,0 +1,122 @@
+;;; test-wttrin-query.el --- Tests for wttrin-query -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2025 Craig Jennings
+
+;;; Commentary:
+
+;; Unit tests for wttrin-query function.
+;; Tests the async weather query orchestration: buffer creation,
+;; loading state, cache lookup, and display callback.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin)
+(require 'testutil-wttrin)
+
+;;; Setup and Teardown
+
+(defun test-wttrin-query-setup ()
+  "Setup for wttrin-query tests."
+  (testutil-wttrin-setup)
+  (when (get-buffer "*wttr.in*")
+    (kill-buffer "*wttr.in*")))
+
+(defun test-wttrin-query-teardown ()
+  "Teardown for wttrin-query tests."
+  (testutil-wttrin-teardown)
+  (when (get-buffer "*wttr.in*")
+    (kill-buffer "*wttr.in*")))
+
+;;; Normal Cases
+
+(ert-deftest test-wttrin-query-normal-creates-buffer ()
+  "Calling query should create the *wttr.in* buffer."
+  (test-wttrin-query-setup)
+  (unwind-protect
+      (cl-letf (((symbol-function 'wttrin--get-cached-or-fetch)
+                 (lambda (_location _callback) nil)))
+        (wttrin-query "Paris")
+        (should (get-buffer "*wttr.in*")))
+    (test-wttrin-query-teardown)))
+
+(ert-deftest test-wttrin-query-normal-shows-loading-message ()
+  "Buffer should show a loading message with the location name while fetching."
+  (test-wttrin-query-setup)
+  (unwind-protect
+      (cl-letf (((symbol-function 'wttrin--get-cached-or-fetch)
+                 (lambda (_location _callback) nil)))
+        (wttrin-query "New Orleans, LA")
+        (with-current-buffer "*wttr.in*"
+          (let ((contents (buffer-string)))
+            (should (string-match-p "Loading" contents))
+            (should (string-match-p "New Orleans, LA" contents)))))
+    (test-wttrin-query-teardown)))
+
+(ert-deftest test-wttrin-query-normal-buffer-is-read-only-during-loading ()
+  "The loading buffer should be read-only to prevent user edits."
+  (test-wttrin-query-setup)
+  (unwind-protect
+      (cl-letf (((symbol-function 'wttrin--get-cached-or-fetch)
+                 (lambda (_location _callback) nil)))
+        (wttrin-query "Tokyo")
+        (with-current-buffer "*wttr.in*"
+          (should buffer-read-only)))
+    (test-wttrin-query-teardown)))
+
+(ert-deftest test-wttrin-query-normal-fetches-for-correct-location ()
+  "Query should request weather for the specified location."
+  (test-wttrin-query-setup)
+  (unwind-protect
+      (let ((fetched-location nil))
+        (cl-letf (((symbol-function 'wttrin--get-cached-or-fetch)
+                   (lambda (location _callback)
+                     (setq fetched-location location))))
+          (wttrin-query "Berlin, DE")
+          (should (equal fetched-location "Berlin, DE"))))
+    (test-wttrin-query-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-wttrin-query-boundary-dead-buffer-callback-is-safe ()
+  "If the buffer is killed before the async callback fires, it should not error."
+  (test-wttrin-query-setup)
+  (unwind-protect
+      (let ((saved-callback nil))
+        (cl-letf (((symbol-function 'wttrin--get-cached-or-fetch)
+                   (lambda (_location callback)
+                     (setq saved-callback callback))))
+          (wttrin-query "Paris")
+          ;; Kill the buffer before callback fires
+          (kill-buffer "*wttr.in*")
+          ;; Invoke callback — should not error
+          (should-not (get-buffer "*wttr.in*"))
+          (funcall saved-callback "weather data")
+          ;; Buffer should NOT be recreated
+          (should-not (get-buffer "*wttr.in*"))))
+    (test-wttrin-query-teardown)))
+
+;;; Error Cases
+
+(ert-deftest test-wttrin-query-error-nil-response-shows-error-message ()
+  "When fetch returns nil, the user should see an error message, not a crash."
+  (test-wttrin-query-setup)
+  (unwind-protect
+      (let ((saved-callback nil)
+            (displayed-message nil))
+        (cl-letf (((symbol-function 'wttrin--get-cached-or-fetch)
+                   (lambda (_location callback)
+                     (setq saved-callback callback)))
+                  ((symbol-function 'message)
+                   (lambda (fmt &rest args)
+                     (setq displayed-message (apply #'format fmt args)))))
+          (wttrin-query "BadLocation")
+          ;; Simulate fetch returning nil
+          (funcall saved-callback nil)
+          ;; Should have shown error message (from wttrin--display-weather validation)
+          (should displayed-message)
+          (should (string-match-p "Cannot retrieve" displayed-message))))
+    (test-wttrin-query-teardown)))
+
+(provide 'test-wttrin-query)
+;;; test-wttrin-query.el ends here