Add a test for Locale#{minimize,maximize}.

test/intl402/Locale/likely-subtags.js

+// Copyright 2018 André Bargull; Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-intl.locale
+description: >
+    Verifies canonicalization, minimization and maximization of specific tags.
+info: |
+    Intl.Locale.prototype.maximize ()
+    3. Let maximal be the result of the Add Likely Subtags algorithm applied to loc.[[Locale]].
+
+    Intl.Locale.prototype.minimize ()
+    3. Let minimal be the result of the Remove Likely Subtags algorithm applied to loc.[[Locale]].
+features: [Intl.Locale]
+---*/
+
+const testDataMaximal = {
+    // Language subtag is present.
+    "en": "en-Latn-US",
+
+    // Language and script subtags are present.
+    "en-Latn": "en-Latn-US",
+    "en-Shaw": "en-Shaw-GB",
+    "en-Arab": "en-Arab-US",
+
+    // Language and region subtags are present.
+    "en-US": "en-Latn-US",
+    "en-GB": "en-Latn-GB",
+    "en-FR": "en-Latn-FR",
+
+    // Language, script, and region subtags are present.
+    "it-Kana-CA": "it-Kana-CA",
+
+    // Undefined primary language.
+    "und": "en-Latn-US",
+    "und-Thai": "th-Thai-TH",
+    "und-419": "es-Latn-419",
+    "und-150": "ru-Cyrl-RU",
+    "und-AT": "de-Latn-AT",
+
+    // privateuse only.
+    "x-private": "x-private",
+};
+
+const testDataMinimal = {
+    // Language subtag is present.
+    "en": "en",
+
+    // Language and script subtags are present.
+    "en-Latn": "en",
+    "ar-Arab": "ar",
+
+    // Language and region subtags are present.
+    "en-US": "en",
+    "en-GB": "en-GB",
+
+    // Reverse cases from |testDataMaximal|.
+    "en-Latn-US": "en",
+    "en-Shaw-GB": "en-Shaw",
+    "en-Arab-US": "en-Arab",
+    "en-Latn-GB": "en-GB",
+    "en-Latn-FR": "en-FR",
+    "it-Kana-CA": "it-Kana-CA",
+    "th-Thai-TH": "th",
+    "es-Latn-419": "es-419",
+    "ru-Cyrl-RU": "ru",
+    "de-Latn-AT": "de-AT",
+
+    // privateuse only.
+    "x-private": "x-private",
+};
+
+// Add variants, extensions, and privateuse subtags and ensure they don't
+// modify the result of the likely subtags algorithms.
+const extras = [
+    "",
+    "-fonipa",
+    "-a-not-assigned",
+    "-u-attr",
+    "-u-co",
+    "-u-co-phonebk",
+    "-x-private",
+];
+
+for (const [tag, maximal] of Object.entries(testDataMaximal)) {
+    assert.sameValue(new Intl.Locale(maximal).maximize().toString(), maximal,
+                     `"${maximal}" should be maximal`);
+
+    for (const extra of extras) {
+        const input = tag + extra;
+        const output = maximal + extra;
+        assert.sameValue(new Intl.Locale(input).maximize().toString(), output,
+                         `"${input}".maximize() should be "${output}"`);
+    }
+}
+
+for (const [tag, minimal] of Object.entries(testDataMinimal)) {
+    assert.sameValue(new Intl.Locale(minimal).minimize().toString(), minimal,
+                     `"${minimal}" should be minimal`);
+
+    for (const extra of extras) {
+        const input = tag + extra;
+        const output = minimal + extra;
+        assert.sameValue(new Intl.Locale(input).minimize().toString(), output,
+                         `"${input}".minimize() should be "${output}"`);
+    }
+}