feat(emacs): Add asynchronous weather fetching to wttrin

Introduce asynchronous data fetching to the wttrin.el Emacs package.
This enhancement avoids blocking Emacs during data retrieval by
using `url-retrieve` for async calls. The behavior is controlled via
a new customizable variable `wttrin-use-async`. Tests have been
added for the new async behavior to ensure proper functionality.feat:makefile): Add package initialization for Emacs batch

Enhance Makefile with package support by loading and initializing
MELPA archive before validating and compiling, ensuring required
packages are available during these operations.

feat(tests): Add unit tests for `wttrin--display-weather`

Introduce comprehensive tests for `wttrin--display-weather` function
to validate buffer creation, content, keybindings, and error
handling.

1 files changed, 213 insertions, 0 deletions

diff --git a/tests/test-wttrin--display-weather.el b/tests/test-wttrin--display-weather.el
new file mode 100644
index 0000000..364908f
--- /dev/null
+++ b/tests/test-wttrin--display-weather.el
@@ -0,0 +1,213 @@
+;;; test-wttrin--display-weather.el --- Tests for wttrin--display-weather -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2025 Craig Jennings
+
+;;; Commentary:
+
+;; Unit tests for wttrin--display-weather function.
+;; Tests the extracted display logic that formats and shows weather data.
+
+;;; Code:
+
+(require 'ert)
+(require 'wttrin)
+(require 'testutil-wttrin)
+
+;;; Test Data Fixtures
+
+(defconst test-wttrin--display-weather-sample-raw-data
+  "
+Weather report: Paris, France
+
+                                                       ┌─────────────┐
+                                                  ┌──────────────────────────┐
+   ┌──────────────────────────────┬───────────────────────────────────────────┴───────────────────────────────────────┐
+   │            Monday             └──────────────────────────────────────────────────────────────────────────────────────┤
+   │                                         2025-11-04 08:00:00 CST
+   │
+   │        Coordinates: 48.8566, 2.3522
+   │
+     \\  /       Partly cloudy
+   _ /\".-. 22 °C
+     \\_(   ).  ↓ 15 km/h
+     /(___(__)  10 km
+                0.0 mm"
+  "Sample raw weather data with realistic wttr.in structure for testing.")
+
+;;; Test Setup and Teardown
+
+(defun test-wttrin--display-weather-setup ()
+  "Setup for display weather tests."
+  (testutil-wttrin-setup)
+  ;; Kill any existing weather buffer
+  (when (get-buffer "*wttr.in*")
+    (kill-buffer "*wttr.in*")))
+
+(defun test-wttrin--display-weather-teardown ()
+  "Teardown for display weather tests."
+  (testutil-wttrin-teardown)
+  ;; Clean up weather buffer
+  (when (get-buffer "*wttr.in*")
+    (kill-buffer "*wttr.in*")))
+
+;;; Normal Cases
+
+(ert-deftest test-wttrin--display-weather-normal-valid-data-creates-buffer ()
+  "Test that valid weather data creates and displays buffer correctly."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        (wttrin--display-weather "Paris, France" test-wttrin--display-weather-sample-raw-data)
+
+        ;; Buffer should exist
+        (should (get-buffer "*wttr.in*"))
+
+        ;; Buffer should be displayed
+        (should (get-buffer-window "*wttr.in*"))
+
+        ;; Buffer should have content
+        (with-current-buffer "*wttr.in*"
+          (should (> (buffer-size) 0))
+
+          ;; Buffer should be read-only
+          (should buffer-read-only)
+
+          ;; Location should be set
+          (should (equal wttrin--current-location "Paris, France"))))
+    (test-wttrin--display-weather-teardown)))
+
+(ert-deftest test-wttrin--display-weather-normal-valid-data-sets-keybindings ()
+  "Test that keybindings are properly set up in weather buffer."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        (wttrin--display-weather "London" test-wttrin--display-weather-sample-raw-data)
+
+        (with-current-buffer "*wttr.in*"
+          ;; Check that keybindings are set (they should be in the local map)
+          (should (keymapp (current-local-map)))
+          (should (commandp (lookup-key (current-local-map) "q")))
+          (should (commandp (lookup-key (current-local-map) "r")))
+          (should (commandp (lookup-key (current-local-map) "g")))))
+    (test-wttrin--display-weather-teardown)))
+
+(ert-deftest test-wttrin--display-weather-normal-valid-data-contains-instructions ()
+  "Test that help instructions are displayed at bottom of buffer."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        (wttrin--display-weather "Tokyo" test-wttrin--display-weather-sample-raw-data)
+
+        (with-current-buffer "*wttr.in*"
+          (goto-char (point-max))
+          (forward-line -2)
+          ;; Should contain help text
+          (should (search-forward "Press:" nil t))
+          (should (search-forward "[g] to query another location" nil t))
+          (should (search-forward "[r] to refresh" nil t))
+          (should (search-forward "[q] to quit" nil t))))
+    (test-wttrin--display-weather-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-wttrin--display-weather-boundary-empty-location-name-creates-buffer ()
+  "Test that empty location name still creates buffer."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        (wttrin--display-weather "" test-wttrin--display-weather-sample-raw-data)
+
+        ;; Buffer should still be created
+        (should (get-buffer "*wttr.in*"))
+
+        (with-current-buffer "*wttr.in*"
+          ;; Location should be set to empty string
+          (should (equal wttrin--current-location ""))))
+    (test-wttrin--display-weather-teardown)))
+
+(ert-deftest test-wttrin--display-weather-boundary-location-with-special-chars-creates-buffer ()
+  "Test that location with special characters creates buffer."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        (wttrin--display-weather "São Paulo, BR 🌆" test-wttrin--display-weather-sample-raw-data)
+
+        (should (get-buffer "*wttr.in*"))
+
+        (with-current-buffer "*wttr.in*"
+          ;; Location with Unicode should be preserved
+          (should (equal wttrin--current-location "São Paulo, BR 🌆"))))
+    (test-wttrin--display-weather-teardown)))
+
+(ert-deftest test-wttrin--display-weather-boundary-empty-string-creates-buffer ()
+  "Test that empty weather string creates buffer without error.
+Empty string does not match ERROR pattern, so it's processed as data."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        (wttrin--display-weather "Paris" "")
+
+        ;; Empty string is not treated as error, buffer is created
+        (should (get-buffer "*wttr.in*"))
+
+        (with-current-buffer "*wttr.in*"
+          ;; Buffer exists but will have minimal/broken content
+          ;; Just verify it was created and made read-only
+          (should buffer-read-only)))
+    (test-wttrin--display-weather-teardown)))
+
+;;; Error Cases
+
+(ert-deftest test-wttrin--display-weather-error-nil-raw-string-shows-message ()
+  "Test that nil raw-string displays error message."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        ;; Capture message output
+        (let ((message-log-max t)
+              (message-displayed nil))
+          (cl-letf (((symbol-function 'message)
+                     (lambda (format-string &rest args)
+                       (setq message-displayed (apply #'format format-string args)))))
+            (wttrin--display-weather "InvalidCity" nil)
+
+            ;; Should display error message
+            (should message-displayed)
+            (should (string-match-p "Cannot retrieve" message-displayed)))))
+    (test-wttrin--display-weather-teardown)))
+
+(ert-deftest test-wttrin--display-weather-error-string-with-error-shows-message ()
+  "Test that weather string containing ERROR shows error message."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        (let ((message-log-max t)
+              (message-displayed nil))
+          (cl-letf (((symbol-function 'message)
+                     (lambda (format-string &rest args)
+                       (setq message-displayed (apply #'format format-string args)))))
+            (wttrin--display-weather "BadLocation" testutil-wttrin-sample-error-response)
+
+            ;; Should display error message
+            (should message-displayed)
+            (should (string-match-p "Cannot retrieve" message-displayed)))))
+    (test-wttrin--display-weather-teardown)))
+
+(ert-deftest test-wttrin--display-weather-error-nil-raw-string-no-buffer-created ()
+  "Test that nil raw-string does not create weather buffer."
+  (test-wttrin--display-weather-setup)
+  (unwind-protect
+      (progn
+        ;; Suppress message output
+        (cl-letf (((symbol-function 'message) (lambda (&rest _) nil)))
+          (wttrin--display-weather "InvalidCity" nil)
+
+          ;; Buffer should not be created for error case
+          ;; (or if it exists from before, it shouldn't be switched to)
+          ;; This is testing the error path doesn't create/switch to buffer
+          (should-not (string-match-p "wttr.in"
+                                      (buffer-name (current-buffer))))))
+    (test-wttrin--display-weather-teardown)))
+
+(provide 'test-wttrin--display-weather)
+;;; test-wttrin--display-weather.el ends here