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+;;; test-calendar-sync--parse-exception-event.el --- Tests for one-event exception parsing  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Unit tests for calendar-sync--parse-exception-event, the per-VEVENT half of
+;; calendar-sync--collect-recurrence-exceptions: it turns a single RECURRENCE-ID
+;; override VEVENT into an exception plist (or nil).  One function per file.
+
+;;; Code:
+
+(require 'ert)
+(add-to-list 'load-path (expand-file-name "." (file-name-directory load-file-name)))
+(add-to-list 'load-path (expand-file-name "../modules" (file-name-directory load-file-name)))
+(require 'testutil-calendar-sync)
+(require 'calendar-sync)
+
+(defun test-cs-parse-exc--override-event (start end)
+  "Return a RECURRENCE-ID override VEVENT string for START..END."
+  (concat "BEGIN:VEVENT\n"
+          "UID:override@google.com\n"
+          "RECURRENCE-ID:20260203T090000Z\n"
+          "SUMMARY:Rescheduled Meeting\n"
+          "DTSTART:" (test-calendar-sync-ics-datetime start) "\n"
+          "DTEND:" (test-calendar-sync-ics-datetime end) "\n"
+          "END:VEVENT"))
+
+;;; Normal Cases
+
+(ert-deftest test-calendar-sync--parse-exception-event-normal-returns-plist ()
+  "Normal: a RECURRENCE-ID override parses into a plist with its overridden times."
+  (let* ((start (test-calendar-sync-time-days-from-now 7 10 0))
+         (end (test-calendar-sync-time-days-from-now 7 11 0))
+         (plist (calendar-sync--parse-exception-event
+                 (test-cs-parse-exc--override-event start end))))
+    (should plist)
+    (should (plist-get plist :recurrence-id))
+    (should (equal "20260203T090000Z" (plist-get plist :recurrence-id-raw)))
+    (should (plist-get plist :start))
+    (should (plist-get plist :end))
+    (should (equal "Rescheduled Meeting" (plist-get plist :summary)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-calendar-sync--parse-exception-event-boundary-no-recurrence-id ()
+  "Boundary: a VEVENT with no RECURRENCE-ID is not an override and returns nil."
+  (let* ((start (test-calendar-sync-time-days-from-now 7 10 0))
+         (end (test-calendar-sync-time-days-from-now 7 11 0))
+         (event (test-calendar-sync-make-vevent "Regular Event" start end)))
+    (should-not (calendar-sync--parse-exception-event event))))
+
+;;; Error Cases
+
+(ert-deftest test-calendar-sync--parse-exception-event-error-unparseable-times ()
+  "Error: a RECURRENCE-ID override whose times do not parse returns nil rather
+than a half-built plist."
+  (let ((event (concat "BEGIN:VEVENT\n"
+                       "UID:broken@google.com\n"
+                       "RECURRENCE-ID:not-a-timestamp\n"
+                       "SUMMARY:Broken Override\n"
+                       "DTSTART:also-garbage\n"
+                       "END:VEVENT")))
+    (should-not (calendar-sync--parse-exception-event event))))
+
+(provide 'test-calendar-sync--parse-exception-event)
+;;; test-calendar-sync--parse-exception-event.el ends here