Intl.DurationFormat update coverage (#3501)

* constructor tests coverage
* add localeMatcher tests
* add styles and numbering system tests
* re-organize folder and files structure

test/intl402/DurationFormat/constructor-locales-invalid.js

@@ -0,0 +1,17 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Checks error cases for the locales argument to the DurationFormat constructor.
+info: |
+    Intl.DurationFormat  ( [ locales [ , options ] ] )
+    (...)
+    3. Let _requestedLocales_ be ? CanonicalizeLocaleList(_locales_).
+includes: [testIntl.js]
+features: [Intl.DurationFormat]
+---*/
+
+for (const [locales, expectedError] of getInvalidLocaleArguments()) {
+    assert.throws(expectedError, function() { new Intl.DurationFormat(locales) })
+}

test/intl402/DurationFormat/constructor-locales-valid.js

@@ -0,0 +1,34 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Checks  cases for the locales argument to the DurationFormat constructor.
+info: |
+    Intl.DurationFormat  ( [ locales [ , options ] ] )
+    (...)
+    3. Let _requestedLocales_ be ? CanonicalizeLocaleList(_locales_).
+features: [Intl.DurationFormat]
+---*/
+
+const defaultLocale = new Intl.DurationFormat().resolvedOptions().locale;
+
+const matchers = ["lookup", "best fit"]
+
+const tests = [
+  [undefined, defaultLocale, "undefined"],
+  ["EN", "en", "Single value"],
+  [[], defaultLocale, "Empty array"],
+  [["en", "EN"], "en", "Duplicate value (canonical first)"],
+  [["EN", "en"], "en", "Duplicate value (canonical last)"],
+  [{ 0: "DE", length: 0 }, defaultLocale, "Object with zero length"],
+  [{ 0: "DE", length: 1 }, "de", "Object with length"],
+];
+
+
+for (const [locales, expected, name] of tests) {
+  matchers.forEach((matcher)=>{
+    const drf = new Intl.DurationFormat(locales, {localeMatcher: matcher});
+    assert.sameValue(drf.resolvedOptions().locale, expected, name);
+  });
+};

test/intl402/DurationFormat/constructor-options-defaults.js

@@ -0,0 +1,32 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Checks handling of valid options for the DurationFormat constructor.
+info: |
+    Intl.DurationFormat  ( [ locales [ , options ] ] )
+    (...)
+    17. For each row in Table 1, except the header row, in table order, do
+      a. Let styleSlot be the Style Slot value.
+      b. Let displaySlot be the Display Slot value.
+      c. Let unit be the Unit value.
+      d. Let valueList be the Values value.
+      e. Let digitalBase be the Digital Default value.
+      f. Let unitOptions be ? GetUnitOptions(unit, options, style, valueList, digitalBase, prevStyle).
+      g. Set durationFormat.[[<styleSlot>]] to unitOptions.[[Style]].
+      h. Set durationFormat.[[<displaySlot>]] to unitOptions.[[Display]].
+features: [Intl.DurationFormat]
+includes: [testIntl.js]
+---*/
+
+testOption( Intl.DurationFormat, "years", "string", ["long", "short", "narrow"], "narrow");
+testOption( Intl.DurationFormat, "months", "string", ["long", "short", "narrow"], "narrow");
+testOption( Intl.DurationFormat, "weeks", "string", ["long", "short", "narrow"], "narrow");
+testOption( Intl.DurationFormat, "days", "string", ["long", "short", "narrow", "numeric", "2-digit"], "numeric");
+testOption( Intl.DurationFormat, "hours", "string", ["long", "short", "narrow", "numeric", "2-digit"], "numeric");
+testOption( Intl.DurationFormat, "minutes", "string", ["long", "short", "narrow", "numeric", "2-digit"], "numeric");
+testOption( Intl.DurationFormat, "milliseconds", "string", ["long", "short", "narrow", "numeric", "2-digit"], "numeric");
+testOption( Intl.DurationFormat, "microseconds", "string", ["long", "short", "narrow", "numeric", "2-digit"], "numeric");
+testOption( Intl.DurationFormat, "nanoseconds", "string", ["long", "short", "narrow", "numeric", "2-digit"], "numeric");
+

test/intl402/DurationFormat/constructor-options-fractionalDigits-invalid.js

@@ -0,0 +1,23 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Tests that the option localeMatcher is processed correctly.
+info: |
+    Intl.DurationFormat ( [ locales [ , options ] ] )
+    (...)
+    18. Set durationFormat.[[FractionalDigits]] to ? GetNumberOption(options, "fractionalDigits", 0, 9, undefined).
+features: [Intl.DurationFormat]
+---*/
+
+const invalidOptions = [
+  -10,
+  10
+];
+
+for (const fractionalDigits of invalidOptions) {
+  assert.throws(RangeError, function() {
+    new Intl.DurationFormat("en", { fractionalDigits });
+  }, `new Intl.DurationFormat("en", {fractionalDigits: "${fractionalDigits}"}) throws RangeError`);
+}

test/intl402/DurationFormat/constructor-options-fractionalDigits-valid.js

@@ -0,0 +1,25 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Tests that the option localeMatcher is processed correctly.
+info: |
+    Intl.DurationFormat ( [ locales [ , options ] ] )
+    (...)
+    18. Set durationFormat.[[FractionalDigits]] to ? GetNumberOption(options, "fractionalDigits", 0, 9, undefined).
+features: [Intl.DurationFormat]
+---*/
+
+const validOptions = [
+  undefined,
+  0,
+  1,
+  5,
+  9
+];
+
+for (const fractionalDigits of validOptions) {
+  const obj = new Intl.DurationFormat("en", {fractionalDigits});
+  assert.sameValue(obj.resolvedOptions().fractionalDigits, fractionalDigits, `${fractionalDigits} is supported by DurationFormat`);
+}

test/intl402/DurationFormat/constructor-options-invalid.js

@@ -0,0 +1,16 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Checks handling of a null options argument to the DurationFormat constructor.
+info: |
+    Intl.DurationFormat ( [ locales [ , options ] ] )
+    (...)
+    4. Let options be GetOptionsObject(options).
+features: [Intl.DurationFormat]
+---*/
+
+assert.sameValue(typeof Intl.DurationFormat, "function");
+
+assert.throws(TypeError, function() { new Intl.DurationFormat([], null) })

test/intl402/DurationFormat/constructor-options-localeMatcher-invalid.js

@@ -0,0 +1,30 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Checks handling of invalid value for the localeMatcher option to the DurationFormat constructor.
+info: |
+    Intl.DurationFormat ( [ locales [ , options ] ] )
+    (...)
+    5. Let matcher be ? GetOption(options, "localeMatcher", "string", « "lookup", "best fit" », "best fit").
+features: [Intl.DurationFormat]
+---*/
+
+const invalidOptions = [
+  null,
+  1,
+  "",
+  "Lookup",
+  "LOOKUP",
+  "lookup\0",
+  "Best fit",
+  "BEST FIT",
+  "best\u00a0fit",
+];
+
+for (const localeMatcher of invalidOptions) {
+  assert.throws(RangeError, function() {
+    new Intl.DurationFormat([], { localeMatcher });
+  }, `${localeMatcher} is an invalid localeMatcher option value`);
+}

test/intl402/DurationFormat/constructor-options-localeMatcher-valid.js

@@ -0,0 +1,15 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Tests that the option localeMatcher is processed correctly.
+info: |
+    Intl.DurationFormat ( [ locales [ , options ] ] )
+    (...)
+    5. Let matcher be ? GetOption(options, "localeMatcher", "string", « "lookup", "best fit" », "best fit").
+features: [Intl.DurationFormat]
+includes: [testIntl.js]
+---*/
+
+testOption(Intl.DurationFormat, "localeMatcher", "string", ["lookup", "best fit"], "best fit", {noReturn: true});

test/intl402/DurationFormat/constructor-options-numberingSystem-invalid.js

@@ -0,0 +1,36 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: >
+    Checks error cases for the options argument to the DurationFormat constructor.
+info: |
+    Intl.DurationFormat ( [ locales [ , options ] ] )
+    (...)
+    6. Let numberingSystem be ? GetOption(options, "numberingSystem", "string", undefined, undefined).
+    7. If numberingSystem does not match the Unicode Locale Identifier type nonterminal, throw a RangeError exception.
+features: [Intl.DurationFormat]
+---*/
+
+const invalidOptions = [
+  "",
+  "a",
+  "ab",
+  "abcdefghi",
+  "abc-abcdefghi",
+  "!invalid!",
+  "-latn-",
+  "latn-",
+  "latn--",
+  "latn-ca",
+  "latn-ca-",
+  "latn-ca-gregory",
+  "latné",
+  "latn编号",
+];
+for (const numberingSystem of invalidOptions) {
+  assert.throws(RangeError, function() {
+    new Intl.DurationFormat('en', {numberingSystem});
+  }, `new Intl.DurationFormat("en", {numberingSystem: "${numberingSystem}"}) throws RangeError`);
+}

test/intl402/DurationFormat/constructor-options-numberingSystem-valid.js

@@ -0,0 +1,21 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: >
+    Checks error cases for the options argument to the DurationFormat constructor.
+info: |
+    Intl.DurationFormat ( [ locales [ , options ] ] )
+    (...)
+    6. Let numberingSystem be ? GetOption(options, "numberingSystem", "string", undefined, undefined).
+    7. If numberingSystem does not match the Unicode Locale Identifier type nonterminal, throw a RangeError exception.
+features: [Intl.DurationFormat]
+---*/
+
+const numberingSystems = Intl.supportedValuesOf("numberingSystem");
+
+for (const numberingSystem of numberingSystems) {
+  const obj = new Intl.DurationFormat("en", {numberingSystem});
+  assert.sameValue(obj.resolvedOptions().numberingSystem, numberingSystem, `${numberingSystem} is supported by DurationFormat`);
+}

test/intl402/DurationFormat/constructor-options-order.js

@@ -0,0 +1,41 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Checks the order of operations on the options argument to the DurationFormat constructor.
+info: |
+    Intl.DurationFormat ( [ locales [ , options ] ] )
+    (...)
+    5. Let matcher be ? GetOption(options, "localeMatcher", "string", « "lookup", "best fit" », "best fit").
+    6. Let numberingSystem be ? GetOption(options, "numberingSystem", "string", undefined, undefined).
+    13. Let style be ? GetOption(options, "style", "string", « "long", "short", "narrow", "digital" », "long").
+includes: [compareArray.js]
+features: [Intl.DurationFormat]
+---*/
+
+var actual = [];
+
+const options = {
+  get localeMatcher() {
+    actual.push("localeMatcher");
+    return undefined;
+  },
+  get numberingSystem() {
+    actual.push("numberingSystem");
+    return undefined;
+  },
+  get style() {
+    actual.push("style");
+    return undefined;
+  },
+};
+
+const expected = [
+  "localeMatcher",
+  "numberingSystem",
+  "style"
+];
+
+let nf = new Intl.DurationFormat(undefined, options);
+assert.compareArray(actual, expected);

test/intl402/DurationFormat/constructor-options-style-invalid.js

@@ -0,0 +1,37 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Checks handling of invalid value for the style option to the DurationFormat constructor.
+info: |
+    InitializeDurationFormat (DurationFormat, locales, options)
+    (...)
+    13. Let style be ? GetOption(options, "style", "string", « "long", "short", "narrow", "digital" », "long").
+    14. Set durationFormat.[[Style]] to style.
+features: [Intl.DurationFormat]
+---*/
+
+const invalidOptions = [
+  null,
+  1,
+  "",
+  "Long",
+  "LONG",
+  "long\0",
+  "Short",
+  "SHORT",
+  "short\0",
+  "Narrow",
+  "NARROW",
+  "narrow\0",
+  "Digital",
+  "DIGITAL",
+  "digital\0",
+];
+
+for (const invalidOption of invalidOptions) {
+  assert.throws(RangeError, function() {
+    new Intl.DurationFormat([], {"style": invalidOption});
+  }, `${invalidOption} is an invalid style option value`);
+}

test/intl402/DurationFormat/constructor-options-style-valid.js

@@ -0,0 +1,31 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: Checks handling of valid values for the style option to the DurationFormat constructor.
+info: |
+    InitializeDurationFormat (DurationFormat, locales, options)
+    (...)
+    13. Let style be ? GetOption(options, "style", "string", « "long", "short", "narrow", "digital" », "long").
+    14. Set durationFormat.[[Style]] to style.
+features: [Intl.DurationFormat]
+---*/
+
+const validOptions = [
+  [undefined, "long"],
+  ["long", "long"],
+  ["short", "short"],
+  ["narrow", "narrow"],
+  ["digital", "digital"],
+  [{ toString() { return "short"; } }, "short"],
+  [{ toString() { return "long"; } }, "long"],
+  [{ toString() { return "narrow"; } }, "narrow"],
+  [{ toString() { return "digital"; } }, "digital"],
+];
+
+for (const [validOption, expected] of validOptions) {
+  const df = new Intl.DurationFormat([], {"style": validOption});
+  const resolvedOptions = df.resolvedOptions();
+  assert.sameValue(resolvedOptions.style, expected);
+}

test/intl402/DurationFormat/newtarget-undefined.js

@@ -0,0 +1,27 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat
+description: >
+    Verifies the NewTarget check for Intl.DurationFormat.
+info: |
+    Intl.DurationFormat ([ locales [ , options ]])
+    (...)
+    1. If NewTarget is undefined, throw a TypeError exception.
+features: [Intl.DurationFormat]
+---*/
+
+assert.sameValue(typeof Intl.DurationFormat, "function");
+
+assert.throws(TypeError, function() {
+  Intl.DurationFormat();
+});
+
+assert.throws(TypeError, function() {
+  Intl.DurationFormat("en");
+});
+
+assert.throws(TypeError, function() {
+  Intl.DurationFormat("not-valid-tag");
+});

test/intl402/DurationFormat/supportedLocalesOf/basic.js

@@ -0,0 +1,19 @@
+// Copyright 2022 Igalia S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.supportedLocalesOf
+description: Tests that Intl.DurationFormat has a supportedLocalesOf property, and it works as expected.
+features: [Intl.DurationFormat]
+---*/
+
+assert.sameValue(typeof Intl.DurationFormat.supportedLocalesOf, "function",
+                 "supportedLocalesOf should be supported.");
+
+const defaultLocale = new Intl.DurationFormat().resolvedOptions().locale;
+const notSupported = "zxx"; // "no linguistic content"
+const requestedLocales = [defaultLocale, notSupported];
+
+const supportedLocales = Intl.DurationFormat.supportedLocalesOf(requestedLocales);
+assert.sameValue(supportedLocales.length, 1, "The length of the supported locales list should be 1");
+assert.sameValue(supportedLocales[0], defaultLocale, "The default locale is returned in the supported list.");

test/intl402/DurationFormat/supportedLocalesOf/branding.js

@@ -0,0 +1,32 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.supportedLocalesOf
+description: >
+    Verifies there's no branding check for Intl.DurationFormat.supportedLocalesOf().
+info: |
+    Intl.DurationFormat.supportedLocalesOf ( locales [, options ])
+features: [Intl.DurationFormat]
+---*/
+
+const supportedLocalesOf = Intl.DurationFormat.supportedLocalesOf;
+
+assert.sameValue(typeof supportedLocalesOf, "function");
+
+const thisValues = [
+  undefined,
+  null,
+  true,
+  "",
+  Symbol(),
+  1,
+  {},
+  Intl.DurationFormat,
+  Intl.DurationFormat.prototype,
+];
+
+for (const thisValue of thisValues) {
+  const result = supportedLocalesOf.call(thisValue);
+  assert.sameValue(Array.isArray(result), true);
+}

test/intl402/DurationFormat/supportedLocalesOf/length.js

@@ -0,0 +1,22 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.supportedLocalesOf
+description: >
+    Checks the "length" property of Intl.DurationFormat.supportedLocalesOf().
+info: |
+    The value of the length property of the supportedLocalesOf method is 1.
+    Unless specified otherwise in this document, the objects, functions, and constructors described in this standard are subject to the generic requirements and restrictions specified for standard built-in ECMAScript objects in the ECMAScript 2019 Language Specification, 10th edition, clause 17, or successor.
+    Every built-in function object, including constructors, has a length property whose value is an integer.
+    Unless otherwise specified, the length property of a built-in function object has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true }.
+includes: [propertyHelper.js]
+features: [Intl.DurationFormat]
+---*/
+
+verifyProperty(Intl.DurationFormat.supportedLocalesOf, "length", {
+  value: 1,
+  writable: false,
+  enumerable: false,
+  configurable: true,
+});

test/intl402/DurationFormat/supportedLocalesOf/locales-empty.js

@@ -0,0 +1,19 @@
+// Copyright 2022 Igalia S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.supportedLocalesOf
+description: Checks handling of an empty locales argument to the supportedLocalesOf function.
+info: |
+    Intl.DurationFormat.supportedLocalesOf ( locales [, options ])
+    (...)
+    3. Return ? SupportedLocales(availableLocales, requestedLocales, options).
+includes: [compareArray.js]
+features: [Intl.DurationFormat]
+---*/
+
+assert.sameValue(typeof Intl.DurationFormat.supportedLocalesOf, "function",
+                 "Should support Intl.DurationFormat.supportedLocalesOf.");
+
+assert.compareArray(Intl.DurationFormat.supportedLocalesOf(), []);
+assert.compareArray(Intl.DurationFormat.supportedLocalesOf([]), []);

test/intl402/DurationFormat/supportedLocalesOf/locales-invalid.js

@@ -0,0 +1,20 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.supportedLocalesOf
+description: Checks error cases for the locales argument to the supportedLocalesOf function.
+info: |
+    Intl.DurationFormat.supportedLocalesOf ( locales [, options ])
+    (...)
+    2. Let requestedLocales be CanonicalizeLocaleList(locales).
+includes: [testIntl.js]
+features: [Intl.DurationFormat]
+---*/
+
+assert.sameValue(typeof Intl.DurationFormat.supportedLocalesOf, "function",
+                 "Should support Intl.DurationFormat.supportedLocalesOf.");
+
+for (const [locales, expectedError] of getInvalidLocaleArguments()) {
+    assert.throws(expectedError, () => Intl.DurationFormat.supportedLocalesOf(locales));
+}

test/intl402/DurationFormat/supportedLocalesOf/locales-specific.js

@@ -0,0 +1,22 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.supportedLocalesOf
+description: Checks handling of specific locales arguments to the supportedLocalesOf function.
+info: |
+    Intl.DurationFormat.supportedLocalesOf ( locales [, options ])
+    (...)
+    3. Return ? SupportedLocales(availableLocales, requestedLocales, options).
+includes: [compareArray.js]
+locale: [sr, sr-Thai-RS, de, zh-CN]
+features: [Intl.DurationFormat]
+---*/
+
+assert.sameValue(typeof Intl.DurationFormat.supportedLocalesOf, "function",
+                 "Should support Intl.DurationFormat.supportedLocalesOf.");
+
+assert.compareArray(Intl.DurationFormat.supportedLocalesOf("sr"), ["sr"]);
+
+const multiLocale = ["sr-Thai-RS", "de", "zh-CN"];
+assert.compareArray(Intl.DurationFormat.supportedLocalesOf(multiLocale, {localeMatcher: "lookup"}), multiLocale);

test/intl402/DurationFormat/supportedLocalesOf/name.js

@@ -0,0 +1,21 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.supportedLocalesOf
+description: >
+    Checks the "name" property of Intl.DurationFormat.supportedLocalesOf().
+info: |
+    Unless specified otherwise in this document, the objects, functions, and constructors described in this standard are subject to the generic requirements and restrictions specified for standard built-in ECMAScript objects in the ECMAScript 2019 Language Specification, 10th edition, clause 17, or successor.
+    Every built-in function object, including constructors, that is not identified as an anonymous function has a name property whose value is a String. Unless otherwise specified, this value is the name that is given to the function in this specification.
+    Unless otherwise specified, the name property of a built-in function object, if it exists, has the attributes { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true }.
+includes: [propertyHelper.js]
+features: [Intl.DurationFormat]
+---*/
+
+verifyProperty(Intl.DurationFormat.supportedLocalesOf, "name", {
+  value: "supportedLocalesOf",
+  writable: false,
+  enumerable: false,
+  configurable: true,
+});

test/intl402/DurationFormat/supportedLocalesOf/prop-desc.js

@@ -0,0 +1,29 @@
+// Copyright 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.supportedLocalesOf
+description: >
+    Checks the "supportedLocalesOf" property of the DurationFormat prototype object.
+info: |
+    Intl.DurationFormat.supportedLocalesOf ( locales [, options ])
+
+    Unless specified otherwise in this document, the objects, functions, and constructors described in this standard are subject to the generic requirements and restrictions specified for standard built-in ECMAScript objects in the ECMAScript 2019 Language Specification, 10th edition, clause 17, or successor.
+
+    Every other data property described in clauses 18 through 26 and in Annex B.2 has the attributes { [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true } unless otherwise specified.
+includes: [propertyHelper.js]
+features: [Intl.DurationFormat]
+---*/
+
+assert.sameValue(
+  typeof Intl.DurationFormat.supportedLocalesOf,
+  "function",
+  "typeof Intl.DurationFormat.supportedLocalesOf is function"
+);
+
+verifyProperty(Intl.DurationFormat, "supportedLocalesOf", {
+  writable: true,
+  enumerable: false,
+  configurable: true,
+});
+