diff --git a/test/intl402/DisplayNames/prototype/of/type-language-valid.js b/test/intl402/DisplayNames/prototype/of/type-language-valid.js
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+++ b/test/intl402/DisplayNames/prototype/of/type-language-valid.js
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+// Copyright (C) 2023 Igalia S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-Intl.DisplayNames.prototype.of
+description: Returns string value for valid `language` codes
+features: [Intl.DisplayNames]
+---*/
+
+
+/*
+unicode_language_id = "root"    // not allowed in ES
+                      | (unicode_language_subtag
+                        (sep unicode_script_subtag)?
+                      | unicode_script_subtag)
+                      (sep unicode_region_subtag)?
+                      (sep unicode_variant_subtag)*
+ */
+
+// unicode_language_subtag = alpha{2,3} | alpha{5,8} ;
+
+var languages = [ { subtag: 'ab', description: '2 letter language_subtag' }, 
+                  { subtag: 'cde', description: '3 letter language_subtag' },
+                  { subtag: 'zzzzzzzz', description: '8 letter language_subtag'} ];
+
+// unicode_script_subtag = alpha{4} ;
+var scripts = [  {subtag: 'abcd', description: '4 letter script_subtag' },
+                 {subtag: '', description: ''} ];
+
+// unicode_region_subtag = (alpha{2} | digit{3}) ;
+var regions = [ {subtag: 'ab', description: '2 letter region_subtag' },
+                {subtag: '123', description: '3 digit region_subtag'},
+                {subtag: '', description: ''} ];
+
+// unicode_variant_subtag = (alphanum{5, 8} | digit alphanum{3}
+
+var variants = [  {subtag: 'abcde', description: '5 letter variant_subtag'}, 
+                  {subtag: 'fghijklm', description: '8 letter variant_subtag'}, 
+                  {subtag: '12345', description: '5 digit variant_subtag'},
+                  {subtag: '1nopq', description: '5 chararcter leading digit variant_subtag'},
+                  {subtag: '12345678', description: '8 digit variant_subtag'}, 
+                  {subtag: 'a2345678', description: '8 character trailing digit variant_subtag'}, 
+                  {subtag: '1abc', description: 'leading digit 4 character variant_subtag' },
+                  {subtag: '2345', description: '4 digit variant_subtag'},
+                  {subtag: '6d7e', description: 'leading digit 4 character mixed alphanum variant_subtag'},
+                  {subtag: '', description: ''} ];
+
+
+function notEmpty(subtag) {
+  return subtag !== '';
+}
+
+var displayNames = new Intl.DisplayNames(undefined, {type: 'language'});
+
+for (var l in languages) {
+  for (var s in scripts) {
+    for (var r in regions) {
+      for (var v in variants) {
+        var languageTag = [languages[l].subtag, scripts[s].subtag, regions[r].subtag, variants[v].subtag].filter(notEmpty).join('-');
+        var languageDescription = [languages[l].description, scripts[s].description, regions[r].description, variants[v].description].filter(notEmpty).join(', '); 
+
+        assert.sameValue(typeof displayNames.of(languageTag), 'string', languageDescription + ": " + languageTag);
+        if (variants[v].subtag !== ''){
+          for (var vAdditional in variants){
+            if (variants[vAdditional].subtag !== '' && vAdditional !== v){
+              languageTag += '-' + variants[vAdditional].subtag;
+              languageDescription += ", " + variants[vAdditional].description;
+              assert.sameValue(typeof displayNames.of(languageTag), 'string', languageDescription + ": " + languageTag);
+            }
+          }
+        }
+      }
+    }
+  }
+}