testing/org-test.el: New helper function `org-test-get-day-name'

* testing/org-test.el (org-test-get-day-name): New function to convert
English day name to current locale.
* testing/lisp/test-org-clock.el (test-org-clock/org-clock-timestamps-change):
(test-org-clock/clock-drawer-dwim): Use the new function instead of
direct `aref'.

testing/lisp/test-org-clock.el

@@ -91,8 +91,8 @@ the buffer."
 
 (ert-deftest test-org-clock/org-clock-timestamps-change ()
   "Test `org-clock-timestamps-change' specifications."
-  (let ((sun (aref org-test-day-of-weeks-abbrev 0))
+  (let ((sun (org-test-get-day-name "Sun"))
-        (mon (aref org-test-day-of-weeks-abbrev 1)))
+        (mon (org-test-get-day-name "Mon")))
     (should
      (equal
       (format "CLOCK: [2023-02-19 %s 21:30]--[2023-02-19 %s 23:35] =>  2:05"
@@ -318,7 +318,7 @@ the buffer."
 
 (ert-deftest test-org-clock/clock-drawer-dwim ()
   "Test DWIM update of days for clocks in logbook drawers."
-  (let ((thu (aref org-test-day-of-weeks-abbrev 4)))
+  (let ((thu (org-test-get-day-name "Thu")))
     (should (equal (format "* Foo
 :LOGBOOK:
 CLOCK: [2022-11-03 %s 06:00]--[2022-11-03 %s 06:01] =>  0:01

testing/org-test.el

@@ -572,6 +572,23 @@ See `org-test-day-of-weeks-seconds'.")
   "Vector of full names for days of week.
 See `org-test-day-of-weeks-seconds'.")
 
+(defun org-test-get-day-name (day &optional full)
+  "Return string containing locale-specific DAY abbrev.
+DAY Should be Mon, Tue, ...
+When FULL is non-nil, return the full name like Monday, Tuesday, ..."
+  (aref
+   (if full org-test-day-of-weeks-full
+     org-test-day-of-weeks-abbrev)
+   (pcase day
+     ((or "Sun" "Sunday") 0)
+     ((or "Mon" "Monday") 1)
+     ((or "Tue" "Tuesday") 2)
+     ((or "Wed" "Wednesday") 3)
+     ((or "Thu" "Thursday") 4)
+     ((or "Fri" "Friday") 5)
+     ((or "Sat" "Saturday") 6)
+     (_ (error "Unknown day of week: %s" day)))))
+
 (provide 'org-test)
 
 ;;; org-test.el ends here