test(calendar-sync): add 32 tests for recurrence exceptions, helpers, unfolding

Cover occurrence-matches-exception-p (6), apply-single-exception (6),
exdate-matches-p (6), extract-cn (5), extract-email (4), unfold-continuation (5).

1 files changed, 67 insertions, 0 deletions

diff --git a/tests/test-calendar-sync--apply-single-exception.el b/tests/test-calendar-sync--apply-single-exception.el
new file mode 100644
index 00000000..2fcf7c71
--- /dev/null
+++ b/tests/test-calendar-sync--apply-single-exception.el
@@ -0,0 +1,67 @@
+;;; test-calendar-sync--apply-single-exception.el --- Tests for exception application -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for calendar-sync--apply-single-exception.
+;; Applies exception overrides to an occurrence plist, returning a modified copy.
+
+;;; Code:
+
+(require 'ert)
+(require 'testutil-calendar-sync)
+(require 'calendar-sync)
+
+;;; Normal Cases
+
+(ert-deftest test-calendar-sync--apply-single-exception-normal-updates-time ()
+  "Exception start/end override the occurrence times."
+  (let ((occ (list :start '(2026 3 15 14 0) :end '(2026 3 15 15 0)
+                   :summary "Standup" :uid "abc"))
+        (exc (list :start '(2026 3 15 16 0) :end '(2026 3 15 17 0))))
+    (let ((result (calendar-sync--apply-single-exception occ exc)))
+      (should (equal '(2026 3 15 16 0) (plist-get result :start)))
+      (should (equal '(2026 3 15 17 0) (plist-get result :end))))))
+
+(ert-deftest test-calendar-sync--apply-single-exception-normal-updates-summary ()
+  "Exception with summary overrides the occurrence summary."
+  (let ((occ (list :start '(2026 3 15 14 0) :summary "Original"))
+        (exc (list :start '(2026 3 15 14 0) :summary "Modified")))
+    (let ((result (calendar-sync--apply-single-exception occ exc)))
+      (should (equal "Modified" (plist-get result :summary))))))
+
+(ert-deftest test-calendar-sync--apply-single-exception-normal-preserves-unset-fields ()
+  "Fields not present in exception are preserved from occurrence."
+  (let ((occ (list :start '(2026 3 15 14 0) :summary "Keep" :uid "abc"
+                   :location "Room 1"))
+        (exc (list :start '(2026 3 15 16 0))))
+    (let ((result (calendar-sync--apply-single-exception occ exc)))
+      (should (equal "Keep" (plist-get result :summary)))
+      (should (equal "abc" (plist-get result :uid)))
+      (should (equal "Room 1" (plist-get result :location))))))
+
+;;; Boundary Cases
+
+(ert-deftest test-calendar-sync--apply-single-exception-boundary-nil-end ()
+  "Exception without :end preserves occurrence :end."
+  (let ((occ (list :start '(2026 3 15 14 0) :end '(2026 3 15 15 0)))
+        (exc (list :start '(2026 3 15 16 0))))
+    (let ((result (calendar-sync--apply-single-exception occ exc)))
+      (should (equal '(2026 3 15 15 0) (plist-get result :end))))))
+
+(ert-deftest test-calendar-sync--apply-single-exception-boundary-does-not-mutate ()
+  "Original occurrence plist is not mutated."
+  (let ((occ (list :start '(2026 3 15 14 0) :summary "Original"))
+        (exc (list :start '(2026 3 15 16 0) :summary "Changed")))
+    (calendar-sync--apply-single-exception occ exc)
+    (should (equal "Original" (plist-get occ :summary)))))
+
+;;; Error Cases
+
+(ert-deftest test-calendar-sync--apply-single-exception-error-empty-exception ()
+  "Exception with no fields still returns a valid plist with occurrence data."
+  (let ((occ (list :start '(2026 3 15 14 0) :summary "Keep"))
+        (exc (list :start nil)))
+    (let ((result (calendar-sync--apply-single-exception occ exc)))
+      (should (equal "Keep" (plist-get result :summary))))))
+
+(provide 'test-calendar-sync--apply-single-exception)
+;;; test-calendar-sync--apply-single-exception.el ends here