Test that Intl.DateTimeFormat canonicalizes the timezones "Etc/GMT",

"Etc/UTC", and "GMT" to "UTC"

test/intl402/DateTimeFormat/canonicalize-utc-timezone.js

@@ -0,0 +1,26 @@
+// Copyright 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-createdatetimeformat
+description: Tests that the time zone names "Etc/UTC", "Etc/GMT", and "GMT" all resolve to "UTC".
+info: |
+  CreateDateTimeFormat ( dateTimeFormat, locales, options, required, default )
+
+  29. If IsTimeZoneOffsetString(timeZone) is true, then
+  ...
+  30. Else,
+    a. Let timeZoneIdentifierRecord be GetAvailableNamedTimeZoneIdentifier(timeZone).
+
+  GetAvailableNamedTimeZoneIdentifier ( timeZoneIdentifier )
+
+  ...
+  5. For each element identifier of identifiers, do
+  ...
+    c. If primary is one of "Etc/UTC", "Etc/GMT", or "GMT", set primary to "UTC".
+---*/
+
+const utcIdentifiers = ["Etc/GMT", "Etc/UTC", "GMT"];
+
+for (const timeZone of utcIdentifiers){
+  assert.sameValue(new Intl.DateTimeFormat([], {timeZone}).resolvedOptions().timeZone, "UTC", "Time zone name " + timeZone + " not canonicalized to 'UTC'.");
+}