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+;;; test-wttrin-mode-initialization-order.el --- Test mode initialization order -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2025 Craig Jennings
+
+;;; Commentary:
+
+;; This test verifies that wttrin--display-weather initializes wttrin-mode
+;; BEFORE setting buffer-local variables. This prevents kill-all-local-variables
+;; (called by derived modes) from wiping out important state like xterm-color--state.
+;;
+;; Bug context: On fresh Emacs launch, weather displayed with no colors because
+;; xterm-color--state was set buffer-local BEFORE wttrin-mode was called, and
+;; wttrin-mode's kill-all-local-variables wiped it out.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin)
+(require 'testutil-wttrin)
+
+(defun test-wttrin-mode-init-setup ()
+  "Setup for mode initialization tests."
+  (testutil-wttrin-setup)
+  (when (get-buffer "*wttr.in*")
+    (kill-buffer "*wttr.in*")))
+
+(defun test-wttrin-mode-init-teardown ()
+  "Teardown for mode initialization tests."
+  (testutil-wttrin-teardown)
+  (when (get-buffer "*wttr.in*")
+    (kill-buffer "*wttr.in*")))
+
+(ert-deftest test-wttrin-mode-initialization-order-mode-before-buffer-local-vars ()
+  "Test that wttrin-mode is activated before setting buffer-local variables.
+
+This test verifies the fix for the color rendering bug where xterm-color--state
+was wiped by kill-all-local-variables.
+
+The test strategy:
+1. Advise wttrin-mode to record when it's called
+2. Advise setq-local to record when buffer-local vars are set
+3. Call wttrin--display-weather
+4. Verify wttrin-mode was called BEFORE any buffer-local vars were set"
+  (test-wttrin-mode-init-setup)
+  (unwind-protect
+      (let ((mode-called-at nil)
+            (first-setq-local-at nil)
+            (call-counter 0))
+
+        ;; Advise to track when wttrin-mode is called
+        (cl-letf (((symbol-function 'wttrin-mode)
+                   (let ((orig-fn (symbol-function 'wttrin-mode)))
+                     (lambda ()
+                       (setq mode-called-at (cl-incf call-counter))
+                       (funcall orig-fn))))
+
+                  ;; Advise to track first buffer-local variable set
+                  ((symbol-function 'set)
+                   (let ((orig-fn (symbol-function 'set)))
+                     (lambda (symbol value)
+                       ;; Track xterm-color--state specifically
+                       (when (and (eq symbol 'xterm-color--state)
+                                  (null first-setq-local-at))
+                         (setq first-setq-local-at (cl-incf call-counter)))
+                       (funcall orig-fn symbol value)))))
+
+          (wttrin--display-weather "Paris" "Test weather data")
+
+          ;; Verify mode was called
+          (should mode-called-at)
+          ;; Verify buffer-local var was set
+          (should first-setq-local-at)
+          ;; Critical: mode must be called BEFORE buffer-local var
+          (should (< mode-called-at first-setq-local-at))))
+
+    (test-wttrin-mode-init-teardown)))
+
+(ert-deftest test-wttrin-mode-initialization-order-xterm-color-state-survives ()
+  "Test that xterm-color--state remains buffer-local after wttrin--display-weather.
+
+This verifies that the state isn't wiped by kill-all-local-variables."
+  (test-wttrin-mode-init-setup)
+  (unwind-protect
+      (progn
+        (wttrin--display-weather "London" "Test data")
+
+        (should (get-buffer "*wttr.in*"))
+
+        (with-current-buffer "*wttr.in*"
+          ;; xterm-color--state should be buffer-local
+          (should (local-variable-p 'xterm-color--state))
+          ;; It should have the correct value
+          (should (eq xterm-color--state :char))))
+
+    (test-wttrin-mode-init-teardown)))
+
+(provide 'test-wttrin-mode-initialization-order)
+;;; test-wttrin-mode-initialization-order.el ends here