Add 94 tests across 10 new test files and fix 2 bugs

New test coverage for previously untested functions:
- filter-day-wide-events, time utilities, day-wide time matching
- make-tooltip, event-is-today, get-tags, done-keywords-predicate
- extract-title, propertize-modeline-string, warn-persistent-failures
- log-silently

Bug fixes discovered by new tests:
- Fix pluralization in no-events tooltip ("1 hours" -> "1 hour", etc.)
- Fix chime--get-tags returning ("") instead of nil for untagged headings

11 files changed, 1553 insertions, 7 deletions

diff --git a/chime.el b/chime.el
index de8a27c..c6455a2 100644
--- a/chime.el
+++ b/chime.el
@@ -1067,10 +1067,12 @@ Returns an alist of (DATE-STRING . EVENTS-LIST)."
   (let* ((hours (/ lookahead-minutes 60))
          (days (/ hours 24))
          (timeframe (cond
-                     ((>= days 7) (format "%d days" days))
-                     ((>= hours 24) (format "%.1f days" (/ hours 24.0)))
-                     ((>= hours 1) (format "%d hours" hours))
-                     (t (format "%d minutes" lookahead-minutes))))
+                     ((>= days 7) (format "%d day%s" days (if (= days 1) "" "s")))
+                     ((>= hours 24) (let ((d (/ hours 24.0)))
+                                      (format "%.1f day%s" d (if (= d 1.0) "" "s"))))
+                     ((>= hours 1) (format "%d hour%s" hours (if (= hours 1) "" "s")))
+                     (t (format "%d minute%s" lookahead-minutes
+                                (if (= lookahead-minutes 1) "" "s")))))
          (header (format-time-string chime-tooltip-header-format))
          (increase-var "chime-tooltip-lookahead-hours"))
     (concat header "\n"
@@ -1240,9 +1242,8 @@ Tooltip shows events within `chime-tooltip-lookahead-hours' hours."
 
 (defun chime--get-tags (marker)
   "Retrieve tags of MARKER."
-  (-> (org-entry-get marker "TAGS")
-      (or "")
-      (org-split-string  ":")))
+  (when-let* ((tags-str (org-entry-get marker "TAGS")))
+    (org-split-string tags-str ":")))
 
 (defun chime--whitelist-predicates ()
   "Return list of whitelist predicate functions.
diff --git a/tests/test-chime-day-wide-time-matching.el b/tests/test-chime-day-wide-time-matching.el
new file mode 100644
index 0000000..0e92093
--- /dev/null
+++ b/tests/test-chime-day-wide-time-matching.el
@@ -0,0 +1,150 @@
+;;; test-chime-day-wide-time-matching.el --- Tests for day-wide time matching -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for day-wide time matching functions:
+;; - chime-current-time-matches-time-of-day-string
+;; - chime-current-time-is-day-wide-time
+;;
+;; These functions determine when to fire notifications for all-day events
+;; by comparing the current time to configured alert times like "08:00".
+;;
+;; IMPORTANT: Mock times must be computed BEFORE entering with-test-time,
+;; because test-time-today-at calls current-time internally.
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;; Load test utilities
+(require 'testutil-general (expand-file-name "testutil-general.el"))
+(require 'testutil-time (expand-file-name "testutil-time.el"))
+
+;;;; Tests for chime-current-time-matches-time-of-day-string
+
+;;; Normal Cases
+
+(ert-deftest test-chime-time-matches-string-exact-match ()
+  "Should return truthy when current time matches the time-of-day string."
+  (let ((mock-time (test-time-today-at 8 0)))
+    (with-test-time mock-time
+      (should (chime-current-time-matches-time-of-day-string "8:00")))))
+
+(ert-deftest test-chime-time-matches-string-no-match ()
+  "Should return nil when current time does not match."
+  (let ((mock-time (test-time-today-at 9 0)))
+    (with-test-time mock-time
+      (should-not (chime-current-time-matches-time-of-day-string "8:00")))))
+
+(ert-deftest test-chime-time-matches-string-afternoon ()
+  "Should match afternoon times correctly."
+  (let ((mock-time (test-time-today-at 17 0)))
+    (with-test-time mock-time
+      (should (chime-current-time-matches-time-of-day-string "17:00")))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-time-matches-string-midnight ()
+  "Should match midnight (00:00)."
+  (let ((mock-time (test-time-today-at 0 0)))
+    (with-test-time mock-time
+      (should (chime-current-time-matches-time-of-day-string "0:00")))))
+
+(ert-deftest test-chime-time-matches-string-end-of-day ()
+  "Should match 23:59."
+  (let ((mock-time (test-time-today-at 23 59)))
+    (with-test-time mock-time
+      (should (chime-current-time-matches-time-of-day-string "23:59")))))
+
+(ert-deftest test-chime-time-matches-string-off-by-one-minute ()
+  "One minute off should not match."
+  (let ((mock-time (test-time-today-at 8 1)))
+    (with-test-time mock-time
+      (should-not (chime-current-time-matches-time-of-day-string "8:00")))))
+
+(ert-deftest test-chime-time-matches-string-leading-zero ()
+  "Should match with leading zero in time string (08:00)."
+  (let ((mock-time (test-time-today-at 8 0)))
+    (with-test-time mock-time
+      (should (chime-current-time-matches-time-of-day-string "08:00")))))
+
+;;;; Tests for chime-current-time-is-day-wide-time
+
+;;; Normal Cases
+
+(ert-deftest test-chime-is-day-wide-time-matches-single-entry ()
+  "Should return truthy when current time matches the configured alert time."
+  (let ((mock-time (test-time-today-at 8 0)))
+    (with-test-time mock-time
+      (let ((chime-day-wide-alert-times '("08:00")))
+        (should (chime-current-time-is-day-wide-time))))))
+
+(ert-deftest test-chime-is-day-wide-time-matches-second-entry ()
+  "Should return truthy when current time matches any entry, not just first."
+  (let ((mock-time (test-time-today-at 17 0)))
+    (with-test-time mock-time
+      (let ((chime-day-wide-alert-times '("08:00" "17:00")))
+        (should (chime-current-time-is-day-wide-time))))))
+
+(ert-deftest test-chime-is-day-wide-time-no-match ()
+  "Should return nil when current time matches no configured alert times."
+  (let ((mock-time (test-time-today-at 12 0)))
+    (with-test-time mock-time
+      (let ((chime-day-wide-alert-times '("08:00" "17:00")))
+        (should-not (chime-current-time-is-day-wide-time))))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-is-day-wide-time-empty-list ()
+  "Should return nil when alert times list is empty."
+  (let ((mock-time (test-time-today-at 8 0)))
+    (with-test-time mock-time
+      (let ((chime-day-wide-alert-times '()))
+        (should-not (chime-current-time-is-day-wide-time))))))
+
+(ert-deftest test-chime-is-day-wide-time-nil-list ()
+  "Should return nil when alert times list is nil."
+  (let ((mock-time (test-time-today-at 8 0)))
+    (with-test-time mock-time
+      (let ((chime-day-wide-alert-times nil))
+        (should-not (chime-current-time-is-day-wide-time))))))
+
+(ert-deftest test-chime-is-day-wide-time-matches-first-of-many ()
+  "Should return truthy when matching the first of several alert times."
+  (let ((mock-time (test-time-today-at 8 0)))
+    (with-test-time mock-time
+      (let ((chime-day-wide-alert-times '("08:00" "12:00" "17:00")))
+        (should (chime-current-time-is-day-wide-time))))))
+
+(provide 'test-chime-day-wide-time-matching)
+;;; test-chime-day-wide-time-matching.el ends here
diff --git a/tests/test-chime-event-is-today.el b/tests/test-chime-event-is-today.el
new file mode 100644
index 0000000..112512b
--- /dev/null
+++ b/tests/test-chime-event-is-today.el
@@ -0,0 +1,139 @@
+;;; test-chime-event-is-today.el --- Tests for chime-event-is-today -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for chime-event-is-today function.
+;; This function checks if an event has any timestamps specifically on today's
+;; date (not past days, not future days).
+;;
+;; NOTE: These tests use real dates (not with-test-time) because
+;; chime-event-is-today uses (decode-time) without arguments internally,
+;; which calls the C-level current_time and bypasses Lisp-level mocking.
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;; Load test utilities
+(require 'testutil-general (expand-file-name "testutil-general.el"))
+(require 'testutil-time (expand-file-name "testutil-time.el"))
+
+;;; Helpers — build events at real dates
+
+(defun test--real-today-at (hour minute)
+  "Return Emacs time for the real today at HOUR:MINUTE."
+  (let ((d (decode-time (current-time))))
+    (encode-time 0 minute hour
+                 (decoded-time-day d)
+                 (decoded-time-month d)
+                 (decoded-time-year d))))
+
+(defun test--real-yesterday-at (hour minute)
+  "Return Emacs time for the real yesterday at HOUR:MINUTE."
+  (let ((d (decode-time (time-subtract (current-time) (days-to-time 1)))))
+    (encode-time 0 minute hour
+                 (decoded-time-day d)
+                 (decoded-time-month d)
+                 (decoded-time-year d))))
+
+(defun test--real-tomorrow-at (hour minute)
+  "Return Emacs time for the real tomorrow at HOUR:MINUTE."
+  (let ((d (decode-time (time-add (current-time) (days-to-time 1)))))
+    (encode-time 0 minute hour
+                 (decoded-time-day d)
+                 (decoded-time-month d)
+                 (decoded-time-year d))))
+
+(defun test--make-timed-event (time)
+  "Make an event alist with a single timed timestamp at TIME."
+  (let ((ts (test-timestamp-string time)))
+    `((times . ((,ts . ,time))))))
+
+(defun test--make-all-day-event (time)
+  "Make an event alist with a single all-day timestamp at TIME."
+  (let ((ts (test-timestamp-string time t)))
+    `((times . ((,ts . nil))))))
+
+;;; Normal Cases
+
+(ert-deftest test-chime-event-is-today-timed-event-today ()
+  "A timed event happening today should return truthy."
+  (let ((event (test--make-timed-event (test--real-today-at 14 30))))
+    (should (chime-event-is-today event))))
+
+(ert-deftest test-chime-event-is-today-all-day-event-today ()
+  "An all-day event for today should return truthy."
+  (let ((event (test--make-all-day-event (test--real-today-at 0 0))))
+    (should (chime-event-is-today event))))
+
+(ert-deftest test-chime-event-is-today-yesterday-returns-nil ()
+  "An event from yesterday should return nil."
+  (let ((event (test--make-timed-event (test--real-yesterday-at 14 30))))
+    (should-not (chime-event-is-today event))))
+
+(ert-deftest test-chime-event-is-today-tomorrow-returns-nil ()
+  "An event for tomorrow should return nil."
+  (let ((event (test--make-timed-event (test--real-tomorrow-at 14 30))))
+    (should-not (chime-event-is-today event))))
+
+(ert-deftest test-chime-event-is-today-past-timed-event-today ()
+  "A timed event earlier today (in the past) should return truthy."
+  (let ((event (test--make-timed-event (test--real-today-at 0 1))))
+    (should (chime-event-is-today event))))
+
+(ert-deftest test-chime-event-is-today-future-timed-event-today ()
+  "A timed event later today (in the future) should return truthy."
+  (let ((event (test--make-timed-event (test--real-today-at 23 58))))
+    (should (chime-event-is-today event))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-event-is-today-event-at-2359-today ()
+  "An event at 23:59 today should return truthy."
+  (let ((event (test--make-timed-event (test--real-today-at 23 59))))
+    (should (chime-event-is-today event))))
+
+(ert-deftest test-chime-event-is-today-event-at-0000-today ()
+  "An event at 00:00 today should return truthy."
+  (let ((event (test--make-timed-event (test--real-today-at 0 0))))
+    (should (chime-event-is-today event))))
+
+;;; Error Cases
+
+(ert-deftest test-chime-event-is-today-empty-times-returns-nil ()
+  "An event with no times should return nil."
+  (let ((event '((times . ()))))
+    (should-not (chime-event-is-today event))))
+
+(provide 'test-chime-event-is-today)
+;;; test-chime-event-is-today.el ends here
diff --git a/tests/test-chime-extract-title.el b/tests/test-chime-extract-title.el
new file mode 100644
index 0000000..ad100e0
--- /dev/null
+++ b/tests/test-chime-extract-title.el
@@ -0,0 +1,127 @@
+;;; test-chime-extract-title.el --- Tests for chime--extract-title -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for chime--extract-title function.
+;; This function extracts the title from an org heading at a marker,
+;; stripping TODO keywords, tags, and priority, then sanitizing the result.
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;; Load test utilities
+(require 'testutil-general (expand-file-name "testutil-general.el"))
+
+;;; Normal Cases
+
+(ert-deftest test-chime-extract-title-plain-heading ()
+  "Plain heading should return just the title."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Team Meeting\n")
+    (goto-char (point-min))
+    (should (string= "Team Meeting" (chime--extract-title (point-marker))))))
+
+(ert-deftest test-chime-extract-title-todo-heading ()
+  "TODO heading should strip the keyword, returning only the title."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* TODO Review PR\n")
+    (goto-char (point-min))
+    (should (string= "Review PR" (chime--extract-title (point-marker))))))
+
+(ert-deftest test-chime-extract-title-heading-with-tags ()
+  "Heading with tags should strip the tags."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Team Meeting                                              :work:\n")
+    (goto-char (point-min))
+    (should (string= "Team Meeting" (chime--extract-title (point-marker))))))
+
+(ert-deftest test-chime-extract-title-heading-with-priority ()
+  "Heading with priority should strip the priority cookie."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* TODO [#A] Urgent task\n")
+    (goto-char (point-min))
+    (should (string= "Urgent task" (chime--extract-title (point-marker))))))
+
+(ert-deftest test-chime-extract-title-unicode ()
+  "Heading with unicode characters should be preserved."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Café meeting with André\n")
+    (goto-char (point-min))
+    (should (string= "Café meeting with André" (chime--extract-title (point-marker))))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-extract-title-todo-only-heading ()
+  "Heading with only a TODO keyword and no title text."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* TODO\n")
+    (goto-char (point-min))
+    ;; Should return empty string (nil title is sanitized to "")
+    (should (stringp (chime--extract-title (point-marker))))))
+
+;;; Error Cases - Sanitization
+
+(ert-deftest test-chime-extract-title-unmatched-paren ()
+  "Title with unmatched parenthesis should be sanitized."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Meeting (rescheduled\n")
+    (goto-char (point-min))
+    (let ((title (chime--extract-title (point-marker))))
+      ;; Sanitizer should balance the paren
+      (should (stringp title))
+      (should (string-match-p "rescheduled" title))
+      ;; Should have balanced parens
+      (should (= (cl-count ?\( title)
+                 (cl-count ?\) title))))))
+
+(ert-deftest test-chime-extract-title-unmatched-bracket ()
+  "Title with unmatched bracket should be sanitized."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Review [draft\n")
+    (goto-char (point-min))
+    (let ((title (chime--extract-title (point-marker))))
+      (should (stringp title))
+      (should (= (cl-count ?\[ title)
+                 (cl-count ?\] title))))))
+
+(provide 'test-chime-extract-title)
+;;; test-chime-extract-title.el ends here
diff --git a/tests/test-chime-filter-day-wide-events.el b/tests/test-chime-filter-day-wide-events.el
new file mode 100644
index 0000000..885a10d
--- /dev/null
+++ b/tests/test-chime-filter-day-wide-events.el
@@ -0,0 +1,136 @@
+;;; test-chime-filter-day-wide-events.el --- Tests for chime--filter-day-wide-events -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for chime--filter-day-wide-events function.
+;; This function filters a times alist to keep only entries that have
+;; a time component in their timestamp string (i.e., timed events),
+;; removing all-day events.
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;; Load test utilities
+(require 'testutil-general (expand-file-name "testutil-general.el"))
+(require 'testutil-time (expand-file-name "testutil-time.el"))
+
+;;; Normal Cases
+
+(ert-deftest test-chime-filter-day-wide-events-keeps-timed-event ()
+  "Timed events (with HH:MM) should be kept."
+  (let* ((time (test-time-tomorrow-at 14 30))
+         (ts (test-timestamp-string time))
+         (times (list (cons ts time)))
+         (result (chime--filter-day-wide-events times)))
+    (should (= 1 (length result)))
+    (should (equal (car (car result)) ts))))
+
+(ert-deftest test-chime-filter-day-wide-events-removes-all-day-event ()
+  "All-day events (no HH:MM) should be removed."
+  (let* ((time (test-time-tomorrow-at 0 0))
+         (ts (test-timestamp-string time t)) ;; all-day = t
+         (times (list (cons ts time)))
+         (result (chime--filter-day-wide-events times)))
+    (should (= 0 (length result)))))
+
+(ert-deftest test-chime-filter-day-wide-events-mixed-keeps-only-timed ()
+  "Mixed list should keep only timed events, removing all-day ones."
+  (let* ((timed-time (test-time-tomorrow-at 14 30))
+         (allday-time (test-time-days-from-now 2))
+         (timed-ts (test-timestamp-string timed-time))
+         (allday-ts (test-timestamp-string allday-time t))
+         (times (list (cons timed-ts timed-time)
+                      (cons allday-ts allday-time)))
+         (result (chime--filter-day-wide-events times)))
+    (should (= 1 (length result)))
+    (should (equal (car (car result)) timed-ts))))
+
+(ert-deftest test-chime-filter-day-wide-events-multiple-timed-all-kept ()
+  "Multiple timed events should all be kept."
+  (let* ((time1 (test-time-tomorrow-at 9 0))
+         (time2 (test-time-tomorrow-at 14 30))
+         (time3 (test-time-tomorrow-at 17 0))
+         (times (list (cons (test-timestamp-string time1) time1)
+                      (cons (test-timestamp-string time2) time2)
+                      (cons (test-timestamp-string time3) time3)))
+         (result (chime--filter-day-wide-events times)))
+    (should (= 3 (length result)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-filter-day-wide-events-empty-list ()
+  "Empty times list should return empty list."
+  (should (null (chime--filter-day-wide-events '()))))
+
+(ert-deftest test-chime-filter-day-wide-events-single-timed ()
+  "Single timed event should return list of one."
+  (let* ((time (test-time-tomorrow-at 10 0))
+         (ts (test-timestamp-string time))
+         (result (chime--filter-day-wide-events (list (cons ts time)))))
+    (should (= 1 (length result)))))
+
+(ert-deftest test-chime-filter-day-wide-events-single-all-day ()
+  "Single all-day event should return empty list."
+  (let* ((time (test-time-tomorrow-at 0 0))
+         (ts (test-timestamp-string time t))
+         (result (chime--filter-day-wide-events (list (cons ts time)))))
+    (should (null result))))
+
+(ert-deftest test-chime-filter-day-wide-events-repeating-timed-kept ()
+  "Repeating timestamp with time component should be kept."
+  (let* ((time (test-time-tomorrow-at 9 0))
+         (ts (test-timestamp-repeating time "+1w"))
+         (result (chime--filter-day-wide-events (list (cons ts time)))))
+    (should (= 1 (length result)))))
+
+(ert-deftest test-chime-filter-day-wide-events-repeating-all-day-removed ()
+  "Repeating timestamp without time component should be removed."
+  (let* ((time (test-time-tomorrow-at 0 0))
+         (ts (test-timestamp-repeating time "+1y" t)) ;; all-day repeating
+         (result (chime--filter-day-wide-events (list (cons ts time)))))
+    (should (null result))))
+
+;;; Error Cases
+
+(ert-deftest test-chime-filter-day-wide-events-all-entries-all-day ()
+  "When all entries are all-day, should return empty list."
+  (let* ((time1 (test-time-tomorrow-at 0 0))
+         (time2 (test-time-days-from-now 2))
+         (times (list (cons (test-timestamp-string time1 t) time1)
+                      (cons (test-timestamp-string time2 t) time2)))
+         (result (chime--filter-day-wide-events times)))
+    (should (null result))))
+
+(provide 'test-chime-filter-day-wide-events)
+;;; test-chime-filter-day-wide-events.el ends here
diff --git a/tests/test-chime-get-tags.el b/tests/test-chime-get-tags.el
new file mode 100644
index 0000000..75cad00
--- /dev/null
+++ b/tests/test-chime-get-tags.el
@@ -0,0 +1,158 @@
+;;; test-chime-get-tags.el --- Tests for chime--get-tags and chime-done-keywords-predicate -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for tag extraction and done-keyword predicate:
+;; - chime--get-tags: extracts org tags from a marker
+;; - chime-done-keywords-predicate: checks if heading has a done keyword
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;; Load test utilities
+(require 'testutil-general (expand-file-name "testutil-general.el"))
+
+;;;; Tests for chime--get-tags
+
+;;; Normal Cases
+
+(ert-deftest test-chime-get-tags-single-tag ()
+  "Should extract a single tag from an org heading."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Task                                                        :work:\n")
+    (goto-char (point-min))
+    (let* ((marker (point-marker))
+           (tags (chime--get-tags marker)))
+      (should (member "work" tags)))))
+
+(ert-deftest test-chime-get-tags-multiple-tags ()
+  "Should extract multiple tags from an org heading."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Task                                                 :work:urgent:\n")
+    (goto-char (point-min))
+    (let* ((marker (point-marker))
+           (tags (chime--get-tags marker)))
+      (should (member "work" tags))
+      (should (member "urgent" tags)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-get-tags-no-tags ()
+  "Should return empty/nil list for heading with no tags."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Task without tags\n")
+    (goto-char (point-min))
+    (let* ((marker (point-marker))
+           (tags (chime--get-tags marker)))
+      ;; Should be empty (nil or empty list)
+      (should (null tags)))))
+
+(ert-deftest test-chime-get-tags-heading-with-todo-keyword ()
+  "Should extract tags correctly even with TODO keyword present."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* TODO Task                                                 :meeting:\n")
+    (goto-char (point-min))
+    (let* ((marker (point-marker))
+           (tags (chime--get-tags marker)))
+      (should (member "meeting" tags)))))
+
+;;;; Tests for chime-done-keywords-predicate
+
+;;; Normal Cases
+
+(ert-deftest test-chime-done-predicate-done-keyword ()
+  "DONE heading should return truthy."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* DONE Completed task\n")
+    (goto-char (point-min))
+    (let ((marker (point-marker)))
+      (should (chime-done-keywords-predicate marker)))))
+
+(ert-deftest test-chime-done-predicate-todo-keyword ()
+  "TODO heading should return nil."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* TODO Active task\n")
+    (goto-char (point-min))
+    (let ((marker (point-marker)))
+      (should-not (chime-done-keywords-predicate marker)))))
+
+(ert-deftest test-chime-done-predicate-no-keyword ()
+  "Heading without any TODO keyword should return nil."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* Plain heading\n")
+    (goto-char (point-min))
+    (let ((marker (point-marker)))
+      (should-not (chime-done-keywords-predicate marker)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-done-predicate-custom-done-keywords ()
+  "Custom done keywords (org-done-keywords) should be recognized."
+  (with-temp-buffer
+    (org-mode)
+    ;; CANCELLED is a standard done keyword in many org configs,
+    ;; but org-done-keywords defaults to just ("DONE").
+    ;; Test with the default DONE keyword.
+    (insert "* DONE Task\n")
+    (goto-char (point-min))
+    (let ((marker (point-marker)))
+      (should (member (nth 2 (org-heading-components)) org-done-keywords)))))
+
+(ert-deftest test-chime-done-predicate-heading-with-priority ()
+  "DONE heading with priority should still be detected."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* DONE [#A] High priority done task\n")
+    (goto-char (point-min))
+    (let ((marker (point-marker)))
+      (should (chime-done-keywords-predicate marker)))))
+
+(ert-deftest test-chime-done-predicate-heading-with-tags ()
+  "DONE heading with tags should still be detected."
+  (with-temp-buffer
+    (org-mode)
+    (insert "* DONE Tagged task                                          :work:\n")
+    (goto-char (point-min))
+    (let ((marker (point-marker)))
+      (should (chime-done-keywords-predicate marker)))))
+
+(provide 'test-chime-get-tags)
+;;; test-chime-get-tags.el ends here
diff --git a/tests/test-chime-log-silently.el b/tests/test-chime-log-silently.el
new file mode 100644
index 0000000..e08987f
--- /dev/null
+++ b/tests/test-chime-log-silently.el
@@ -0,0 +1,88 @@
+;;; test-chime-log-silently.el --- Tests for chime--log-silently -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for chime--log-silently function.
+;; This function writes to *Messages* buffer without echoing to minibuffer.
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;;; Normal Cases
+
+(ert-deftest test-chime-log-silently-writes-to-messages ()
+  "Should write the formatted text to *Messages* buffer."
+  (let ((messages-buf (get-buffer-create "*Messages*")))
+    (with-current-buffer messages-buf
+      (let ((pos-before (point-max)))
+        (chime--log-silently "Test log message")
+        (goto-char pos-before)
+        (should (search-forward "Test log message" nil t))))))
+
+(ert-deftest test-chime-log-silently-formats-with-args ()
+  "Should format with args like `format'."
+  (let ((messages-buf (get-buffer-create "*Messages*")))
+    (with-current-buffer messages-buf
+      (let ((pos-before (point-max)))
+        (chime--log-silently "Event count: %d, name: %s" 5 "Meeting")
+        (goto-char pos-before)
+        (should (search-forward "Event count: 5, name: Meeting" nil t))))))
+
+(ert-deftest test-chime-log-silently-multiple-calls-append ()
+  "Multiple calls should append sequentially."
+  (let ((messages-buf (get-buffer-create "*Messages*")))
+    (with-current-buffer messages-buf
+      (let ((pos-before (point-max)))
+        (chime--log-silently "First message")
+        (chime--log-silently "Second message")
+        (goto-char pos-before)
+        (let ((first-pos (search-forward "First message" nil t))
+              (second-pos (progn (goto-char pos-before)
+                                 (search-forward "Second message" nil t))))
+          (should first-pos)
+          (should second-pos)
+          ;; Second should come after first
+          (should (> second-pos first-pos)))))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-log-silently-empty-format-string ()
+  "Empty format string should not error."
+  ;; Should not signal an error
+  (should-not (condition-case nil
+                  (progn (chime--log-silently "") nil)
+                (error t))))
+
+(provide 'test-chime-log-silently)
+;;; test-chime-log-silently.el ends here
diff --git a/tests/test-chime-make-tooltip.el b/tests/test-chime-make-tooltip.el
new file mode 100644
index 0000000..f51a3b3
--- /dev/null
+++ b/tests/test-chime-make-tooltip.el
@@ -0,0 +1,245 @@
+;;; test-chime-make-tooltip.el --- Tests for tooltip generation functions -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for tooltip generation functions:
+;; - chime--make-tooltip
+;; - chime--make-no-events-tooltip
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;; Load test utilities
+(require 'testutil-general (expand-file-name "testutil-general.el"))
+(require 'testutil-time (expand-file-name "testutil-time.el"))
+(require 'testutil-events (expand-file-name "testutil-events.el"))
+
+;;; Setup and Teardown
+
+(defun test-chime-make-tooltip-setup ()
+  "Setup function run before each test."
+  (chime-create-test-base-dir)
+  (setq chime-modeline-tooltip-max-events 5)
+  (setq chime-tooltip-header-format "Upcoming Events as of %a %b %d %Y @ %I:%M %p")
+  (setq chime-display-time-format-string "%I:%M %p")
+  (setq chime-time-left-format-at-event "right now")
+  (setq chime-time-left-format-short "in %M")
+  (setq chime-time-left-format-long "in %H %M"))
+
+(defun test-chime-make-tooltip-teardown ()
+  "Teardown function run after each test."
+  (chime-delete-test-base-dir))
+
+;;; Helper to build upcoming-events list items
+;;; Each item is (EVENT TIME-INFO MINUTES-UNTIL) where
+;;; TIME-INFO is (TIMESTAMP-STR . TIME-OBJECT)
+
+(defun test-make-upcoming-item (title time minutes-until)
+  "Create an upcoming-events list item for TITLE at TIME, MINUTES-UNTIL from now."
+  (let ((ts (test-timestamp-string time)))
+    (list `((title . ,title)
+            (times . ((,ts . ,time)))
+            (intervals . ((10 . medium))))
+          (cons ts time)
+          minutes-until)))
+
+;;;; Tests for chime--make-tooltip
+
+;;; Normal Cases
+
+(ert-deftest test-chime-make-tooltip-single-event ()
+  "Single event should produce tooltip with header, day label, and event line."
+  (test-chime-make-tooltip-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (event-time (time-add now (seconds-to-time 1800))) ;; 30 min
+             (upcoming (list (test-make-upcoming-item "Team Meeting" event-time 30))))
+        (with-test-time now
+          (let ((result (chime--make-tooltip upcoming)))
+            (should (stringp result))
+            ;; Should contain header
+            (should (string-match-p "Upcoming Events" result))
+            ;; Should contain the event title
+            (should (string-match-p "Team Meeting" result))
+            ;; Should contain day separator
+            (should (string-match-p "─────────────" result)))))
+    (test-chime-make-tooltip-teardown)))
+
+(ert-deftest test-chime-make-tooltip-respects-max-events ()
+  "Should respect chime-modeline-tooltip-max-events limit."
+  (test-chime-make-tooltip-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (upcoming (list
+                        (test-make-upcoming-item "Event 1" (time-add now (seconds-to-time 600)) 10)
+                        (test-make-upcoming-item "Event 2" (time-add now (seconds-to-time 1200)) 20)
+                        (test-make-upcoming-item "Event 3" (time-add now (seconds-to-time 1800)) 30)))
+             (chime-modeline-tooltip-max-events 2))
+        (with-test-time now
+          (let ((result (chime--make-tooltip upcoming)))
+            ;; Should show first 2 events
+            (should (string-match-p "Event 1" result))
+            (should (string-match-p "Event 2" result))
+            ;; Should NOT show 3rd event
+            (should-not (string-match-p "Event 3" result))
+            ;; Should show "and 1 more"
+            (should (string-match-p "1 more event" result)))))
+    (test-chime-make-tooltip-teardown)))
+
+(ert-deftest test-chime-make-tooltip-and-n-more-pluralized ()
+  "The 'and N more' text should use correct pluralization."
+  (test-chime-make-tooltip-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (upcoming (list
+                        (test-make-upcoming-item "Event 1" (time-add now (seconds-to-time 600)) 10)
+                        (test-make-upcoming-item "Event 2" (time-add now (seconds-to-time 1200)) 20)
+                        (test-make-upcoming-item "Event 3" (time-add now (seconds-to-time 1800)) 30)
+                        (test-make-upcoming-item "Event 4" (time-add now (seconds-to-time 2400)) 40)))
+             (chime-modeline-tooltip-max-events 2))
+        (with-test-time now
+          (let ((result (chime--make-tooltip upcoming)))
+            ;; 2 remaining - should be "events" (plural)
+            (should (string-match-p "2 more events" result)))))
+    (test-chime-make-tooltip-teardown)))
+
+(ert-deftest test-chime-make-tooltip-nil-max-shows-all ()
+  "When chime-modeline-tooltip-max-events is nil, all events should be shown."
+  (test-chime-make-tooltip-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (upcoming (list
+                        (test-make-upcoming-item "Event 1" (time-add now (seconds-to-time 600)) 10)
+                        (test-make-upcoming-item "Event 2" (time-add now (seconds-to-time 1200)) 20)
+                        (test-make-upcoming-item "Event 3" (time-add now (seconds-to-time 1800)) 30)))
+             (chime-modeline-tooltip-max-events nil))
+        (with-test-time now
+          (let ((result (chime--make-tooltip upcoming)))
+            (should (string-match-p "Event 1" result))
+            (should (string-match-p "Event 2" result))
+            (should (string-match-p "Event 3" result))
+            ;; No "more" text
+            (should-not (string-match-p "more event" result)))))
+    (test-chime-make-tooltip-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-make-tooltip-empty-list-returns-nil ()
+  "Empty event list should return nil."
+  (should (null (chime--make-tooltip '()))))
+
+(ert-deftest test-chime-make-tooltip-nil-returns-nil ()
+  "Nil input should return nil."
+  (should (null (chime--make-tooltip nil))))
+
+(ert-deftest test-chime-make-tooltip-max-events-equals-count ()
+  "When max-events equals event count, no 'more' text should appear."
+  (test-chime-make-tooltip-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (upcoming (list
+                        (test-make-upcoming-item "Event 1" (time-add now (seconds-to-time 600)) 10)
+                        (test-make-upcoming-item "Event 2" (time-add now (seconds-to-time 1200)) 20)))
+             (chime-modeline-tooltip-max-events 2))
+        (with-test-time now
+          (let ((result (chime--make-tooltip upcoming)))
+            (should (string-match-p "Event 1" result))
+            (should (string-match-p "Event 2" result))
+            (should-not (string-match-p "more event" result)))))
+    (test-chime-make-tooltip-teardown)))
+
+;;;; Tests for chime--make-no-events-tooltip
+
+;;; Normal Cases
+
+(ert-deftest test-chime-no-events-tooltip-shows-minutes ()
+  "For less than 60 minutes, should show timeframe in minutes."
+  (let ((result (chime--make-no-events-tooltip 30)))
+    (should (stringp result))
+    (should (string-match-p "30 minutes" result))
+    (should (string-match-p "Left-click: Open calendar" result))))
+
+(ert-deftest test-chime-no-events-tooltip-shows-hours ()
+  "For 2+ hours, should show timeframe in hours."
+  (let ((result (chime--make-no-events-tooltip 120)))
+    (should (stringp result))
+    (should (string-match-p "2 hours" result))))
+
+(ert-deftest test-chime-no-events-tooltip-shows-days ()
+  "For 7+ days, should show timeframe in days."
+  (let ((result (chime--make-no-events-tooltip 10080))) ;; 7 days
+    (should (stringp result))
+    (should (string-match-p "7 days" result))))
+
+(ert-deftest test-chime-no-events-tooltip-shows-fractional-days ()
+  "For 1-7 days (24-167 hours), should show fractional days."
+  (let ((result (chime--make-no-events-tooltip 2160))) ;; 36 hours = 1.5 days
+    (should (stringp result))
+    (should (string-match-p "1\\.5 days" result))))
+
+(ert-deftest test-chime-no-events-tooltip-includes-header ()
+  "Tooltip should include the header from chime-tooltip-header-format."
+  (let ((result (chime--make-no-events-tooltip 60)))
+    (should (string-match-p "Upcoming Events" result))))
+
+(ert-deftest test-chime-no-events-tooltip-mentions-config-var ()
+  "Tooltip should mention chime-tooltip-lookahead-hours for user guidance."
+  (let ((result (chime--make-no-events-tooltip 60)))
+    (should (string-match-p "chime-tooltip-lookahead-hours" result))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-no-events-tooltip-exactly-60-minutes ()
+  "Exactly 60 minutes (1 hour) should say '1 hour' not '1 hours'."
+  (let ((result (chime--make-no-events-tooltip 60)))
+    (should (stringp result))
+    ;; A user expects correct English: "1 hour" not "1 hours"
+    (should (string-match-p "1 hour[^s]" result))))
+
+(ert-deftest test-chime-no-events-tooltip-exactly-1-day ()
+  "Exactly 1440 minutes (24 hours / 1 day) should not say '1.0 days'."
+  (let ((result (chime--make-no-events-tooltip 1440)))
+    (should (stringp result))
+    ;; User expects "1 day" or "1.0 day" — not "1.0 days"
+    (should (string-match-p "1\\.0 day[^s]" result))))
+
+(ert-deftest test-chime-no-events-tooltip-exactly-1-minute ()
+  "1 minute should say '1 minute' not '1 minutes'."
+  (let ((result (chime--make-no-events-tooltip 1)))
+    (should (stringp result))
+    ;; User expects "1 minute" not "1 minutes"
+    (should (string-match-p "1 minute[^s]" result))))
+
+(provide 'test-chime-make-tooltip)
+;;; test-chime-make-tooltip.el ends here
diff --git a/tests/test-chime-propertize-modeline.el b/tests/test-chime-propertize-modeline.el
new file mode 100644
index 0000000..fc210b2
--- /dev/null
+++ b/tests/test-chime-propertize-modeline.el
@@ -0,0 +1,163 @@
+;;; test-chime-propertize-modeline.el --- Tests for chime--propertize-modeline-string -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for chime--propertize-modeline-string function.
+;; This function adds tooltip, click handlers, and mouse-face to modeline text.
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;; Load test utilities
+(require 'testutil-general (expand-file-name "testutil-general.el"))
+(require 'testutil-time (expand-file-name "testutil-time.el"))
+(require 'testutil-events (expand-file-name "testutil-events.el"))
+
+;;; Setup/Teardown
+
+(defun test-chime-propertize-setup ()
+  "Setup function."
+  (chime-create-test-base-dir)
+  (setq chime-tooltip-header-format "Upcoming Events as of %a %b %d %Y @ %I:%M %p")
+  (setq chime-display-time-format-string "%I:%M %p")
+  (setq chime-time-left-format-at-event "right now")
+  (setq chime-time-left-format-short "in %M")
+  (setq chime-time-left-format-long "in %H %M"))
+
+(defun test-chime-propertize-teardown ()
+  "Teardown function."
+  (chime-delete-test-base-dir)
+  (setq chime--upcoming-events nil))
+
+;;; Normal Cases
+
+(ert-deftest test-chime-propertize-adds-help-echo ()
+  "Should add help-echo property (tooltip) when events exist."
+  (test-chime-propertize-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (event-time (time-add now (seconds-to-time 1800)))
+             (ts (test-timestamp-string event-time)))
+        (setq chime--upcoming-events
+              (list (list `((title . "Meeting") (times . ((,ts . ,event-time))))
+                          (cons ts event-time)
+                          30)))
+        (with-test-time now
+          (let ((result (chime--propertize-modeline-string " ⏰ Meeting")))
+            (should (get-text-property 0 'help-echo result)))))
+    (test-chime-propertize-teardown)))
+
+(ert-deftest test-chime-propertize-adds-mouse-face ()
+  "Should add mouse-face property for highlight on hover."
+  (test-chime-propertize-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (event-time (time-add now (seconds-to-time 1800)))
+             (ts (test-timestamp-string event-time)))
+        (setq chime--upcoming-events
+              (list (list `((title . "Meeting") (times . ((,ts . ,event-time))))
+                          (cons ts event-time)
+                          30)))
+        (with-test-time now
+          (let ((result (chime--propertize-modeline-string " ⏰ Meeting")))
+            (should (eq 'mode-line-highlight
+                        (get-text-property 0 'mouse-face result))))))
+    (test-chime-propertize-teardown)))
+
+(ert-deftest test-chime-propertize-adds-keymap ()
+  "Should add local-map with click handlers."
+  (test-chime-propertize-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (event-time (time-add now (seconds-to-time 1800)))
+             (ts (test-timestamp-string event-time)))
+        (setq chime--upcoming-events
+              (list (list `((title . "Meeting") (times . ((,ts . ,event-time))))
+                          (cons ts event-time)
+                          30)))
+        (with-test-time now
+          (let ((result (chime--propertize-modeline-string " ⏰ Meeting")))
+            (should (keymapp (get-text-property 0 'local-map result))))))
+    (test-chime-propertize-teardown)))
+
+(ert-deftest test-chime-propertize-tooltip-contains-event ()
+  "Tooltip text should contain the event title."
+  (test-chime-propertize-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (event-time (time-add now (seconds-to-time 1800)))
+             (ts (test-timestamp-string event-time)))
+        (setq chime--upcoming-events
+              (list (list `((title . "Team Standup") (times . ((,ts . ,event-time))))
+                          (cons ts event-time)
+                          30)))
+        (with-test-time now
+          (let* ((result (chime--propertize-modeline-string " ⏰ Meeting"))
+                 (tooltip (get-text-property 0 'help-echo result)))
+            (should (string-match-p "Team Standup" tooltip)))))
+    (test-chime-propertize-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-propertize-nil-events-returns-plain-text ()
+  "When chime--upcoming-events is nil, should return plain text without properties."
+  (test-chime-propertize-setup)
+  (unwind-protect
+      (let ((chime--upcoming-events nil))
+        (let ((result (chime--propertize-modeline-string " ⏰")))
+          ;; Should return the text as-is
+          (should (string= " ⏰" result))
+          ;; Should NOT have help-echo (no tooltip)
+          (should-not (get-text-property 0 'help-echo result))))
+    (test-chime-propertize-teardown)))
+
+(ert-deftest test-chime-propertize-empty-text ()
+  "Empty string should still get properties when events exist."
+  (test-chime-propertize-setup)
+  (unwind-protect
+      (let* ((now (test-time-now))
+             (event-time (time-add now (seconds-to-time 1800)))
+             (ts (test-timestamp-string event-time)))
+        (setq chime--upcoming-events
+              (list (list `((title . "Meeting") (times . ((,ts . ,event-time))))
+                          (cons ts event-time)
+                          30)))
+        (with-test-time now
+          (let ((result (chime--propertize-modeline-string "")))
+            ;; Even empty string gets propertized
+            (should (stringp result)))))
+    (test-chime-propertize-teardown)))
+
+(provide 'test-chime-propertize-modeline)
+;;; test-chime-propertize-modeline.el ends here
diff --git a/tests/test-chime-time-utilities.el b/tests/test-chime-time-utilities.el
new file mode 100644
index 0000000..06e1a3b
--- /dev/null
+++ b/tests/test-chime-time-utilities.el
@@ -0,0 +1,174 @@
+;;; test-chime-time-utilities.el --- Tests for time utility functions -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for chime time utility functions:
+;; - chime-get-minutes-into-day
+;; - chime-get-hours-minutes-from-time
+;; - chime-set-hours-minutes-for-time
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;; Load test utilities
+(require 'testutil-general (expand-file-name "testutil-general.el"))
+(require 'testutil-time (expand-file-name "testutil-time.el"))
+
+;;;; Tests for chime-get-minutes-into-day
+
+;;; Normal Cases
+
+(ert-deftest test-chime-get-minutes-into-day-noon ()
+  "Noon (12:00) should be 720 minutes into the day."
+  (should (= 720 (chime-get-minutes-into-day "12:00"))))
+
+(ert-deftest test-chime-get-minutes-into-day-afternoon ()
+  "14:30 should be 870 minutes into the day."
+  (should (= 870 (chime-get-minutes-into-day "14:30"))))
+
+(ert-deftest test-chime-get-minutes-into-day-morning ()
+  "8:00 should be 480 minutes into the day."
+  (should (= 480 (chime-get-minutes-into-day "8:00"))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-get-minutes-into-day-midnight ()
+  "Midnight (0:00) should be 0 minutes into the day."
+  (should (= 0 (chime-get-minutes-into-day "0:00"))))
+
+(ert-deftest test-chime-get-minutes-into-day-end-of-day ()
+  "23:59 should be 1439 minutes into the day."
+  (should (= 1439 (chime-get-minutes-into-day "23:59"))))
+
+(ert-deftest test-chime-get-minutes-into-day-one-minute-past-midnight ()
+  "0:01 should be 1 minute into the day."
+  (should (= 1 (chime-get-minutes-into-day "0:01"))))
+
+;;;; Tests for chime-get-hours-minutes-from-time
+
+;;; Normal Cases
+
+(ert-deftest test-chime-get-hours-minutes-afternoon ()
+  "14:30 should return (14 30)."
+  (should (equal '(14 30) (chime-get-hours-minutes-from-time "14:30"))))
+
+(ert-deftest test-chime-get-hours-minutes-morning ()
+  "8:00 should return (8 0)."
+  (should (equal '(8 0) (chime-get-hours-minutes-from-time "8:00"))))
+
+(ert-deftest test-chime-get-hours-minutes-with-minutes ()
+  "9:45 should return (9 45)."
+  (should (equal '(9 45) (chime-get-hours-minutes-from-time "9:45"))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-get-hours-minutes-midnight ()
+  "0:00 should return (0 0)."
+  (should (equal '(0 0) (chime-get-hours-minutes-from-time "0:00"))))
+
+(ert-deftest test-chime-get-hours-minutes-exact-hour ()
+  "10:00 should return (10 0) with no leftover minutes."
+  (should (equal '(10 0) (chime-get-hours-minutes-from-time "10:00"))))
+
+(ert-deftest test-chime-get-hours-minutes-end-of-day ()
+  "23:59 should return (23 59)."
+  (should (equal '(23 59) (chime-get-hours-minutes-from-time "23:59"))))
+
+(ert-deftest test-chime-get-hours-minutes-noon ()
+  "12:00 should return (12 0)."
+  (should (equal '(12 0) (chime-get-hours-minutes-from-time "12:00"))))
+
+;;;; Tests for chime-set-hours-minutes-for-time
+
+;;; Normal Cases
+
+(ert-deftest test-chime-set-hours-minutes-preserves-date ()
+  "Setting hours/minutes should preserve the date."
+  (let* ((base (test-time-tomorrow-at 10 0))
+         (result (chime-set-hours-minutes-for-time base 14 30))
+         (decoded (decode-time result))
+         (base-decoded (decode-time base)))
+    ;; Date should be the same
+    (should (= (decoded-time-day base-decoded) (decoded-time-day decoded)))
+    (should (= (decoded-time-month base-decoded) (decoded-time-month decoded)))
+    (should (= (decoded-time-year base-decoded) (decoded-time-year decoded)))
+    ;; Time should be changed
+    (should (= 14 (decoded-time-hour decoded)))
+    (should (= 30 (decoded-time-minute decoded)))
+    (should (= 0 (decoded-time-second decoded)))))
+
+(ert-deftest test-chime-set-hours-minutes-changes-time ()
+  "Setting different hours/minutes should produce different time."
+  (let* ((base (test-time-tomorrow-at 10 0))
+         (result (chime-set-hours-minutes-for-time base 15 45))
+         (decoded (decode-time result)))
+    (should (= 15 (decoded-time-hour decoded)))
+    (should (= 45 (decoded-time-minute decoded)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-set-hours-minutes-midnight ()
+  "Setting to midnight (0, 0) should work."
+  (let* ((base (test-time-tomorrow-at 10 0))
+         (result (chime-set-hours-minutes-for-time base 0 0))
+         (decoded (decode-time result)))
+    (should (= 0 (decoded-time-hour decoded)))
+    (should (= 0 (decoded-time-minute decoded)))))
+
+(ert-deftest test-chime-set-hours-minutes-end-of-day ()
+  "Setting to 23:59 should work."
+  (let* ((base (test-time-tomorrow-at 10 0))
+         (result (chime-set-hours-minutes-for-time base 23 59))
+         (decoded (decode-time result)))
+    (should (= 23 (decoded-time-hour decoded)))
+    (should (= 59 (decoded-time-minute decoded)))))
+
+(ert-deftest test-chime-set-hours-minutes-roundtrip ()
+  "Extracting hours/minutes and setting them back should produce same time-of-day."
+  (let* ((base (test-time-tomorrow-at 14 30))
+         (hm (chime-get-hours-minutes-from-time "14:30"))
+         (result (chime-set-hours-minutes-for-time base (car hm) (cadr hm)))
+         (decoded (decode-time result)))
+    (should (= 14 (decoded-time-hour decoded)))
+    (should (= 30 (decoded-time-minute decoded)))))
+
+(ert-deftest test-chime-set-hours-minutes-seconds-always-zero ()
+  "Seconds should always be set to 0 regardless of base time."
+  (let* ((base (test-time-now)) ;; may have non-zero seconds internally
+         (result (chime-set-hours-minutes-for-time base 10 0))
+         (decoded (decode-time result)))
+    (should (= 0 (decoded-time-second decoded)))))
+
+(provide 'test-chime-time-utilities)
+;;; test-chime-time-utilities.el ends here
diff --git a/tests/test-chime-warn-persistent-failures.el b/tests/test-chime-warn-persistent-failures.el
new file mode 100644
index 0000000..e24132a
--- /dev/null
+++ b/tests/test-chime-warn-persistent-failures.el
@@ -0,0 +1,165 @@
+;;; test-chime-warn-persistent-failures.el --- Tests for chime--maybe-warn-persistent-failures -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2024-2026 Craig Jennings
+
+;; Author: Craig Jennings <c@cjennings.net>
+
+;; This program is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Unit tests for chime--maybe-warn-persistent-failures function.
+;; This function warns the user when consecutive async failures reach
+;; the configured threshold. It should warn exactly once at the threshold.
+
+;;; Code:
+
+;; Initialize package system for batch mode
+(when noninteractive
+  (package-initialize))
+
+(require 'ert)
+
+;; Load dependencies required by chime
+(require 'dash)
+(require 'alert)
+(require 'async)
+(require 'org-agenda)
+
+;; Load chime from parent directory
+(load (expand-file-name "../chime.el") nil t)
+
+;;; Setup and Teardown
+
+(defun test-warn-failures-setup ()
+  "Setup function."
+  (setq chime--consecutive-async-failures 0)
+  (setq chime-max-consecutive-failures 5))
+
+(defun test-warn-failures-teardown ()
+  "Teardown function."
+  (setq chime--consecutive-async-failures 0)
+  (setq chime-max-consecutive-failures 5))
+
+;;; Normal Cases
+
+(ert-deftest test-chime-warn-failures-warns-at-threshold ()
+  "Should call display-warning when failures reach the threshold."
+  (test-warn-failures-setup)
+  (unwind-protect
+      (let ((warned nil))
+        (setq chime--consecutive-async-failures 5)
+        (setq chime-max-consecutive-failures 5)
+        (cl-letf (((symbol-function 'display-warning)
+                   (lambda (_type _msg &rest _args) (setq warned t))))
+          (chime--maybe-warn-persistent-failures)
+          (should warned)))
+    (test-warn-failures-teardown)))
+
+(ert-deftest test-chime-warn-failures-no-warn-below-threshold ()
+  "Should NOT warn when failures are below the threshold."
+  (test-warn-failures-setup)
+  (unwind-protect
+      (let ((warned nil))
+        (setq chime--consecutive-async-failures 4)
+        (setq chime-max-consecutive-failures 5)
+        (cl-letf (((symbol-function 'display-warning)
+                   (lambda (_type _msg &rest _args) (setq warned t))))
+          (chime--maybe-warn-persistent-failures)
+          (should-not warned)))
+    (test-warn-failures-teardown)))
+
+(ert-deftest test-chime-warn-failures-no-warn-above-threshold ()
+  "Should NOT warn again after exceeding the threshold (warns once)."
+  (test-warn-failures-setup)
+  (unwind-protect
+      (let ((warned nil))
+        (setq chime--consecutive-async-failures 6)
+        (setq chime-max-consecutive-failures 5)
+        (cl-letf (((symbol-function 'display-warning)
+                   (lambda (_type _msg &rest _args) (setq warned t))))
+          (chime--maybe-warn-persistent-failures)
+          (should-not warned)))
+    (test-warn-failures-teardown)))
+
+(ert-deftest test-chime-warn-failures-message-includes-count ()
+  "Warning message should include the failure count."
+  (test-warn-failures-setup)
+  (unwind-protect
+      (let ((warning-msg nil))
+        (setq chime--consecutive-async-failures 5)
+        (setq chime-max-consecutive-failures 5)
+        (cl-letf (((symbol-function 'display-warning)
+                   (lambda (_type msg &rest _args) (setq warning-msg msg))))
+          (chime--maybe-warn-persistent-failures)
+          (should warning-msg)
+          (should (string-match-p "5" warning-msg))))
+    (test-warn-failures-teardown)))
+
+(ert-deftest test-chime-warn-failures-severity-is-warning ()
+  "Warning should use :warning severity."
+  (test-warn-failures-setup)
+  (unwind-protect
+      (let ((warning-severity nil))
+        (setq chime--consecutive-async-failures 5)
+        (setq chime-max-consecutive-failures 5)
+        (cl-letf (((symbol-function 'display-warning)
+                   (lambda (_type _msg &rest args) (setq warning-severity (car args)))))
+          (chime--maybe-warn-persistent-failures)
+          (should (eq :warning warning-severity))))
+    (test-warn-failures-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-chime-warn-failures-threshold-of-1 ()
+  "Threshold of 1 should warn on the very first failure."
+  (test-warn-failures-setup)
+  (unwind-protect
+      (let ((warned nil))
+        (setq chime--consecutive-async-failures 1)
+        (setq chime-max-consecutive-failures 1)
+        (cl-letf (((symbol-function 'display-warning)
+                   (lambda (_type _msg &rest _args) (setq warned t))))
+          (chime--maybe-warn-persistent-failures)
+          (should warned)))
+    (test-warn-failures-teardown)))
+
+(ert-deftest test-chime-warn-failures-threshold-of-0-disables ()
+  "Threshold of 0 should disable warnings entirely."
+  (test-warn-failures-setup)
+  (unwind-protect
+      (let ((warned nil))
+        (setq chime--consecutive-async-failures 0)
+        (setq chime-max-consecutive-failures 0)
+        (cl-letf (((symbol-function 'display-warning)
+                   (lambda (_type _msg &rest _args) (setq warned t))))
+          (chime--maybe-warn-persistent-failures)
+          (should-not warned)))
+    (test-warn-failures-teardown)))
+
+(ert-deftest test-chime-warn-failures-zero-failures-no-warn ()
+  "Zero failures should never warn regardless of threshold."
+  (test-warn-failures-setup)
+  (unwind-protect
+      (let ((warned nil))
+        (setq chime--consecutive-async-failures 0)
+        (setq chime-max-consecutive-failures 5)
+        (cl-letf (((symbol-function 'display-warning)
+                   (lambda (_type _msg &rest _args) (setq warned t))))
+          (chime--maybe-warn-persistent-failures)
+          (should-not warned)))
+    (test-warn-failures-teardown)))
+
+(provide 'test-chime-warn-persistent-failures)
+;;; test-chime-warn-persistent-failures.el ends here