test: add 86 new tests, fix 3 production bugs, fix 8 stale tests

New test coverage (86 tests across 7 files):
- custom-case: 43 tests (title-case-region, upcase-dwim, downcase-dwim)
- custom-datetime: 10 tests (all insert methods with mocked time)
- config-utilities: 11 tests (format-build-time type branching)
- org-capture-config: 22 tests (date-prefix + event-content)

Production bugs found and fixed:
- custom-case: title-case-region crashes on whitespace/punctuation-only input
  (char-after returns nil when no word chars found)
- org-capture-config: browser branch missing empty-string guard on :initial
  plist value, producing stray newline in capture output
- mousetrap-mode: keymap never registered in minor-mode-map-alist, so mode
  was silently not blocking any mouse events. Now pushes/removes on toggle.

Additional fixes:
- local-repository: fix cons cell syntax bug in localrepo-initialize
  (was calling vars as functions instead of using cons)
- dupre-theme tests: update rainbow-delimiter color expectations
- mousetrap tests: update dashboard profile (primary-click → scroll+primary)
- music completion test: bind completion-ignore-case to prevent pollution
- Delete redundant interactive recording test (duplicate of ERT version)

Refactoring:
- org-capture-config: extract cj/org-capture--date-prefix pure function
  from cj/org-capture-format-event-headline for testability

Test checklist: todo.org updated to [11/25], removed untestable modules

1 files changed, 112 insertions, 0 deletions

diff --git a/tests/test-custom-datetime-all-methods.el b/tests/test-custom-datetime-all-methods.el
new file mode 100644
index 00000000..c9cfa41e
--- /dev/null
+++ b/tests/test-custom-datetime-all-methods.el
@@ -0,0 +1,112 @@
+;;; test-custom-datetime-all-methods.el --- Tests for custom-datetime.el -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for all six insert functions in custom-datetime.el.
+;;
+;; All functions follow the same pattern: (insert (format-time-string FMT (current-time)))
+;; They are thin wrappers, so tests focus on:
+;; - Each function inserts text matching its format variable
+;; - Custom format variables are respected
+;; - Trailing space convention is preserved where present
+;;
+;; We mock current-time to a fixed value for deterministic output.
+
+;;; Code:
+
+(require 'ert)
+
+(unless (boundp 'cj/custom-keymap)
+  (defvar cj/custom-keymap (make-sparse-keymap)))
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'custom-datetime)
+
+;; Fixed time: 2026-02-15 14:30:45 CST (UTC-6)
+(defconst test-datetime--fixed-time (encode-time 45 30 14 15 2 2026)
+  "Fixed time value for deterministic tests.")
+
+(defmacro test-datetime--with-fixed-time (&rest body)
+  "Execute BODY with current-time mocked to test-datetime--fixed-time."
+  `(cl-letf (((symbol-function 'current-time)
+              (lambda () test-datetime--fixed-time)))
+     ,@body))
+
+;; Helper: call FUNC in a temp buffer with mocked time and return inserted text
+(defun test-datetime--run (func)
+  "Call FUNC with mocked time and return the buffer contents."
+  (with-temp-buffer
+    (test-datetime--with-fixed-time
+     (funcall func))
+    (buffer-string)))
+
+;;; Normal Cases — Each function inserts expected format
+
+(ert-deftest test-custom-datetime-all-methods-normal-readable-date-time ()
+  "cj/insert-readable-date-time should insert human-readable date and time."
+  (let ((result (test-datetime--run #'cj/insert-readable-date-time)))
+    (should (string-match-p "Sunday, February 15, 2026" result))
+    (should (string-match-p "02:30:45 PM" result))))
+
+(ert-deftest test-custom-datetime-all-methods-normal-sortable-date-time ()
+  "cj/insert-sortable-date-time should insert ISO-style date and time."
+  (let ((result (test-datetime--run #'cj/insert-sortable-date-time)))
+    (should (string-match-p "2026-02-15" result))
+    (should (string-match-p "14:30:45" result))))
+
+(ert-deftest test-custom-datetime-all-methods-normal-sortable-time ()
+  "cj/insert-sortable-time should insert time with AM/PM and timezone."
+  (let ((result (test-datetime--run #'cj/insert-sortable-time)))
+    (should (string-match-p "02:30:45 PM" result))))
+
+(ert-deftest test-custom-datetime-all-methods-normal-readable-time ()
+  "cj/insert-readable-time should insert short time with AM/PM."
+  (let ((result (test-datetime--run #'cj/insert-readable-time)))
+    (should (string-match-p "2:30 PM" result))))
+
+(ert-deftest test-custom-datetime-all-methods-normal-sortable-date ()
+  "cj/insert-sortable-date should insert ISO date with day abbreviation."
+  (let ((result (test-datetime--run #'cj/insert-sortable-date)))
+    (should (string-match-p "2026-02-15 Sun" result))))
+
+(ert-deftest test-custom-datetime-all-methods-normal-readable-date ()
+  "cj/insert-readable-date should insert full human-readable date."
+  (let ((result (test-datetime--run #'cj/insert-readable-date)))
+    (should (equal result "Sunday, February 15, 2026"))))
+
+;;; Boundary Cases
+
+(ert-deftest test-custom-datetime-all-methods-boundary-trailing-space-convention ()
+  "Functions with trailing space in format should include it in output."
+  ;; These formats have trailing spaces by default
+  (let ((result-rdt (test-datetime--run #'cj/insert-readable-date-time))
+        (result-sdt (test-datetime--run #'cj/insert-sortable-date-time))
+        (result-st (test-datetime--run #'cj/insert-sortable-time))
+        (result-rt (test-datetime--run #'cj/insert-readable-time)))
+    (should (string-suffix-p " " result-rdt))
+    (should (string-suffix-p " " result-sdt))
+    (should (string-suffix-p " " result-st))
+    (should (string-suffix-p " " result-rt))))
+
+(ert-deftest test-custom-datetime-all-methods-boundary-no-trailing-space ()
+  "Functions without trailing space in format should not add one."
+  (let ((result-sd (test-datetime--run #'cj/insert-sortable-date))
+        (result-rd (test-datetime--run #'cj/insert-readable-date)))
+    (should-not (string-suffix-p " " result-sd))
+    (should-not (string-suffix-p " " result-rd))))
+
+(ert-deftest test-custom-datetime-all-methods-boundary-custom-format-override ()
+  "Overriding a format variable should change the output."
+  (let ((readable-date-format "%d/%m/%Y"))
+    (should (equal (test-datetime--run #'cj/insert-readable-date)
+                   "15/02/2026"))))
+
+(ert-deftest test-custom-datetime-all-methods-boundary-inserts-at-point ()
+  "Inserted text should appear at point, not replacing buffer contents."
+  (with-temp-buffer
+    (insert "before ")
+    (test-datetime--with-fixed-time
+     (cj/insert-sortable-date))
+    (should (string-prefix-p "before 2026-02-15" (buffer-string)))))
+
+(provide 'test-custom-datetime-all-methods)
+;;; test-custom-datetime-all-methods.el ends here