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+;;; test-browser-config--preferred-default.el --- Tests for the first-run browser pick -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Unit tests for cj/--preferred-default-browser, the pure helper that picks
+;; the first-run default when no saved choice exists.
+;;
+;; The behavior it fixes: EWW is listed first in `cj/browser-definitions' and
+;; carries a nil executable, so `cj/discover-browsers' always reports it as
+;; available and it sorted first.  A fresh machine therefore opened every org
+;; link in the Emacs text browser until the user found cj/choose-browser, even
+;; with Chrome or Firefox installed.  The helper prefers a real external
+;; browser and keeps EWW as the genuine last resort.
+;;
+;; The helper takes the discovered list as an argument rather than calling
+;; `cj/discover-browsers' itself, so these tests drive real data structures
+;; and never stub executable-find.
+;;
+;; Test organization:
+;; - Normal Cases: external browser preferred over a leading built-in
+;; - Boundary Cases: only built-ins, only externals, single entry, empty list
+;; - Error Cases: entries missing the :executable key
+;;
+;;; Code:
+
+(require 'ert)
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'browser-config)
+
+(defconst test-browser--eww
+  '(:executable nil :function eww-browse-url :name "EWW (Emacs Browser)"
+                :path nil :program-var nil))
+
+(defconst test-browser--chrome
+  '(:executable "google-chrome" :function browse-url-chrome :name "Google Chrome"
+                :path "/usr/bin/google-chrome" :program-var browse-url-chrome-program))
+
+(defconst test-browser--firefox
+  '(:executable "firefox" :function browse-url-firefox :name "Firefox"
+                :path "/usr/bin/firefox" :program-var browse-url-firefox-program))
+
+;;; Normal Cases
+
+(ert-deftest test-browser-config-preferred-default-skips-leading-builtin ()
+  "Normal: an installed external browser wins over a built-in listed first."
+  (should (equal (cj/--preferred-default-browser
+                  (list test-browser--eww test-browser--chrome))
+                 test-browser--chrome)))
+
+(ert-deftest test-browser-config-preferred-default-keeps-external-order ()
+  "Normal: the FIRST external in list order wins, not merely any external."
+  (should (equal (cj/--preferred-default-browser
+                  (list test-browser--eww test-browser--chrome test-browser--firefox))
+                 test-browser--chrome)))
+
+;;; Boundary Cases
+
+(ert-deftest test-browser-config-preferred-default-builtin-only-falls-back ()
+  "Boundary: with no external installed, the built-in is still chosen."
+  (should (equal (cj/--preferred-default-browser (list test-browser--eww))
+                 test-browser--eww)))
+
+(ert-deftest test-browser-config-preferred-default-external-only ()
+  "Boundary: a list of externals returns the first one."
+  (should (equal (cj/--preferred-default-browser
+                  (list test-browser--firefox test-browser--chrome))
+                 test-browser--firefox)))
+
+(ert-deftest test-browser-config-preferred-default-empty-list-is-nil ()
+  "Boundary: an empty discovery result yields nil, never an error."
+  (should (null (cj/--preferred-default-browser '()))))
+
+(ert-deftest test-browser-config-preferred-default-single-builtin ()
+  "Boundary: a one-element built-in list returns that element."
+  (should (equal (cj/--preferred-default-browser (list test-browser--eww))
+                 test-browser--eww)))
+
+;;; Error Cases
+
+(ert-deftest test-browser-config-preferred-default-missing-executable-key ()
+  "Error: a plist with no :executable key counts as built-in, not a crash."
+  (let ((malformed '(:name "Odd" :function ignore)))
+    (should (equal (cj/--preferred-default-browser
+                    (list malformed test-browser--chrome))
+                   test-browser--chrome))
+    (should (equal (cj/--preferred-default-browser (list malformed))
+                   malformed))))
+
+(provide 'test-browser-config--preferred-default)
+;;; test-browser-config--preferred-default.el ends here