bug#62420: 29.0.60; fns-tests-collate-strings fails on Cygwin

[Ken Brown]

The test in the subject fails on Cygwin as follows:

Test fns-tests-collate-strings condition:
    (ert-test-failed
     ((should-error
       (string-collate-equalp "xyzzy" "xyzzy" "en_DE.UTF-8"))
      :form
      (string-collate-equalp "xyzzy" "xyzzy" "en_DE.UTF-8")
      :value t :fail-reason "did not signal an error"))

The reason is that en_DE.UTF-8 is actually a valid locale on Cygwin.
[Cygwin gets its locale information from Windows.  The latter supports
the RFC 5646 locale "en-DE", which is called "English (Germany)" in the
"Region" settings.]

The following trivial patch fixes the problem:

--- a/test/src/fns-tests.el
+++ b/test/src/fns-tests.el
@@ -254,7 +254,7 @@ fns-tests-collate-strings
   (should (string-collate-equalp "xyzzy" "XYZZY" nil t))
    ;; Locale must be valid.
-  (should-error (string-collate-equalp "xyzzy" "xyzzy" "en_DE.UTF-8")))
+  (should-error (string-collate-equalp "xyzzy" "xyzzy" "en_XY.UTF-8")))
  ;; There must be a check for valid codepoints.  (Check not 
implemented yet)
 ;  (should-error


Is this OK for the emacs-29 branch?

[Note: The test will still fail on current Cygwin after this patch; but
that's because of a bug in Cygwin, which has been fixed in the
development sources for Cygwin 3.5.]

Ken