diff --git a/.changeset/30335-storage-test-message-locale.md b/.changeset/30335-storage-test-message-locale.md
new file mode 100644
index 00000000000..0953a201223
--- /dev/null
+++ b/.changeset/30335-storage-test-message-locale.md
@@ -0,0 +1,10 @@
+---
+'@objectstack/service-storage': patch
+---
+
+fix(service-storage): Setup → Storage → Test connection answers in the caller's language
+
+Clause-②: no
+Metadata-protocol: none
+
+The `storage/test` settings action writes its `message` in the language the settings action route hands its handler as `locale` (`Accept-Language`, else `?locale`), the same source the mail test notice reads. It covers the sentences the product writes: the success sentence (which still names the adapter), the refusal when the probe read back is not the one written, and the refusal for S3 settings missing a bucket or a region. An adapter's own error text stays verbatim: alone in English, as before; in another language behind a lead-in saying the connection test failed. Every language on the platform locale table is served (`en`, `zh-CN`, `zh-Hant`, `es-ES`, `ar`, `fr`, `pt-BR`, `ru`, `de`, `ja-JP`, `ko`), the caller's code read through `platformLocaleTagOf` and then shortened one subtag at a time; an absent locale, or one the table does not name, is answered in English exactly as before. `ok`, `severity`, the probe and its cleanup, and the operator log lines are unchanged.
diff --git a/packages/services/service-storage/src/storage-service-plugin.ts b/packages/services/service-storage/src/storage-service-plugin.ts
index 38bfdf413d1..59063b6c259 100644
--- a/packages/services/service-storage/src/storage-service-plugin.ts
+++ b/packages/services/service-storage/src/storage-service-plugin.ts
@@ -87,6 +87,7 @@ import { mayActIrreversibly } from '@objectstack/platform-objects/system';
 import { FILE_REFERENCES_MIGRATION_ID } from '@objectstack/spec/system';
 import { inProcessSessionReadInput } from '@objectstack/types';
 import { SwappableStorageService } from './swappable-storage-service.js';
+import { S3SettingsIncompleteError, storageTestCopy } from './storage-test-copy.js';
 import {
   resolveStorageTarget,
   needsStorageSwap,
@@ -286,7 +287,7 @@ export class StorageServicePlugin implements Plugin {
       const bucket = values.s3_bucket as string | undefined;
       const region = values.s3_region as string | undefined;
       if (!bucket || !region) {
-        throw new Error('StorageServicePlugin: S3 adapter requires s3_bucket and s3_region');
+        throw new S3SettingsIncompleteError();
       }
       const opts: S3StorageAdapterOptions = {
         bucket,
@@ -814,7 +815,11 @@ export class StorageServicePlugin implements Plugin {
         // Register the live `storage/test` probe handler.
         if (typeof settings.registerAction === 'function' && this.storage) {
           const proxy = this.storage;
-          settings.registerAction('storage', 'test', async ({ values, payload }: any) => {
+          settings.registerAction('storage', 'test', async ({ values, payload, locale }: any) => {
+            // [#30335] The answer is the toast the administrator reads: written
+            // in the caller's display language, which the settings action
+            // route hands over as `locale` (English when none is given).
+            const copy = storageTestCopy(typeof locale === 'string' ? locale : undefined);
             // Merge the (possibly unsaved) form state posted as
             // `payload.values` over the persisted snapshot so an operator
             // can validate edits before hitting "Save". Matches the
@@ -851,7 +856,10 @@ export class StorageServicePlugin implements Plugin {
               try {
                 target = await this.buildAdapterFromValues(merged);
               } catch (err: any) {
-                return { ok: false, severity: 'error', message: err?.message ?? String(err) };
+                const message = err instanceof S3SettingsIncompleteError
+                  ? copy.s3SettingsIncomplete
+                  : copy.failed(err?.message ?? String(err));
+                return { ok: false, severity: 'error', message };
               }
             }
 
@@ -900,18 +908,18 @@ export class StorageServicePlugin implements Plugin {
                 // unguarded delete, whose failure IS a probe failure the
                 // operator must be told about, and no path deletes twice.
                 await removeProbeObject();
-                return { ok: false, severity: 'error', message: 'Probe download did not match upload.' };
+                return { ok: false, severity: 'error', message: copy.downloadMismatch };
               }
               await target.delete(probeKey);
               const adapter = String(merged.adapter ?? this.options.adapter ?? 'local');
               return {
                 ok: true,
                 severity: 'info',
-                message: `Storage round-trip succeeded (adapter=${adapter}).`,
+                message: copy.succeeded(adapter),
               };
             } catch (err: any) {
               await removeProbeObject();
-              return { ok: false, severity: 'error', message: err?.message ?? String(err) };
+              return { ok: false, severity: 'error', message: copy.failed(err?.message ?? String(err)) };
             }
           });
           ctx.logger.info('StorageServicePlugin: registered settings action storage/test');
diff --git a/packages/services/service-storage/src/storage-test-copy.ts b/packages/services/service-storage/src/storage-test-copy.ts
new file mode 100644
index 00000000000..8d01131d3c5
--- /dev/null
+++ b/packages/services/service-storage/src/storage-test-copy.ts
@@ -0,0 +1,161 @@
+// Copyright (c) 2025 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#30335] The sentences Setup → Storage → 测试连接 (`storage/test`) answers
+ * with, one entry per language on the platform locale table.
+ *
+ * The console prints the action's `message` as the toast, bare, so the
+ * sentence is the administrator's whole answer. The settings action route
+ * hands the handler the caller's display language (`Accept-Language`, else
+ * `?locale`) as the input's `locale`; an absent locale, or one with no entry
+ * here, is answered in English, the sentence every caller got before.
+ *
+ * The table carries every language on the platform locale table
+ * (`@objectstack/spec/system` `PLATFORM_LOCALES`). The four entries this package
+ * served first keep their keys (`zh-CN`, `ja-JP`, `es-ES`); the caller's code is
+ * read through the table's own reader, `platformLocaleTagOf`, so a stored
+ * alias (`zh-TW`, `pt`, `en-US`) and a table tag (`zh-Hans`, `ja`) both find
+ * their entry. A code the table does not name is shortened one subtag at a
+ * time (RFC 4647 lookup: `fr-CA` → `fr`, `zh-Hant-TW` → `zh-Hant`); nothing
+ * left ⇒ English.
+ *
+ * Only the sentences the product writes live here. An adapter's own error
+ * text (the S3 SDK's, the file system's) is passed through verbatim: in
+ * English on its own, as it always was; in another language behind a lead-in
+ * that says the connection test failed, so the reader knows what the
+ * untranslated part is. The operator log lines stay English.
+ */
+
+import { platformLocaleTagOf, type PlatformLocaleTag } from '@objectstack/spec/system';
+
+/** The English refusal for S3 settings missing a bucket or a region. */
+export const S3_SETTINGS_INCOMPLETE_MESSAGE =
+  'StorageServicePlugin: S3 adapter requires s3_bucket and s3_region';
+
+/**
+ * Thrown when the `storage` settings name the S3 adapter without a bucket or a
+ * region. Its message is the English refusal the operator log has always
+ * carried; the `storage/test` answer reads the type to write the refusal in the
+ * caller's language instead.
+ */
+export class S3SettingsIncompleteError extends Error {
+  constructor() {
+    super(S3_SETTINGS_INCOMPLETE_MESSAGE);
+    this.name = 'S3SettingsIncompleteError';
+  }
+}
+
+export interface StorageTestCopy {
+  /** The probe object was written, read back identical and deleted. */
+  succeeded(adapter: string): string;
+  /** The probe object read back is not the one written. */
+  downloadMismatch: string;
+  /** The S3 adapter was chosen without a bucket or a region. */
+  s3SettingsIncomplete: string;
+  /** The adapter refused; `reason` is its own text, verbatim. */
+  failed(reason: string): string;
+}
+
+/** The table's keys: the platform locale table's languages, the first four under their older codes. */
+export type StorageTestCopyLocale =
+  'en' | 'zh-CN' | 'zh-Hant' | 'es-ES' | 'ar' | 'fr' | 'pt-BR' | 'ru' | 'de' | 'ja-JP' | 'ko';
+
+export const STORAGE_TEST_COPY: Record<StorageTestCopyLocale, StorageTestCopy> = {
+  en: {
+    succeeded: (adapter) => `Storage round-trip succeeded (adapter=${adapter}).`,
+    downloadMismatch: 'Probe download did not match upload.',
+    s3SettingsIncomplete: S3_SETTINGS_INCOMPLETE_MESSAGE,
+    failed: (reason) => reason,
+  },
+  'zh-CN': {
+    succeeded: (adapter) => `存储连接测试成功（适配器：${adapter}）。`,
+    downloadMismatch: '探测文件下载后的内容与上传的不一致。',
+    s3SettingsIncomplete: 'S3 适配器需要填写存储桶（s3_bucket）和区域（s3_region）。',
+    failed: (reason) => `存储连接测试失败：${reason}`,
+  },
+  'zh-Hant': {
+    succeeded: (adapter) => `儲存空間連線測試成功（轉接器：${adapter}）。`,
+    downloadMismatch: '探測檔案下載後的內容與上傳的不一致。',
+    s3SettingsIncomplete: 'S3 轉接器需要填寫儲存貯體（s3_bucket）和區域（s3_region）。',
+    failed: (reason) => `儲存空間連線測試失敗：${reason}`,
+  },
+  'ja-JP': {
+    succeeded: (adapter) => `ストレージの接続テストに成功しました（アダプター: ${adapter}）。`,
+    downloadMismatch: 'プローブファイルのダウンロード内容がアップロードした内容と一致しません。',
+    s3SettingsIncomplete: 'S3 アダプターにはバケット（s3_bucket）とリージョン（s3_region）の指定が必要です。',
+    failed: (reason) => `ストレージの接続テストに失敗しました: ${reason}`,
+  },
+  ko: {
+    succeeded: (adapter) => `스토리지 연결 테스트에 성공했습니다(어댑터: ${adapter}).`,
+    downloadMismatch: '다운로드한 테스트 파일이 업로드한 파일과 일치하지 않습니다.',
+    s3SettingsIncomplete: 'S3 어댑터에는 버킷(s3_bucket)과 리전(s3_region)이 필요합니다.',
+    failed: (reason) => `스토리지 연결 테스트에 실패했습니다: ${reason}`,
+  },
+  'es-ES': {
+    succeeded: (adapter) => `La prueba de conexión del almacenamiento se ha completado correctamente (adaptador: ${adapter}).`,
+    downloadMismatch: 'El archivo de prueba descargado no coincide con el que se subió.',
+    s3SettingsIncomplete: 'El adaptador S3 necesita un bucket (s3_bucket) y una región (s3_region).',
+    failed: (reason) => `La prueba de conexión del almacenamiento ha fallado: ${reason}`,
+  },
+  ar: {
+    succeeded: (adapter) => `نجح اختبار الاتصال بالتخزين (المحوّل: ${adapter}).`,
+    downloadMismatch: 'محتوى ملف الاختبار الذي تم تنزيله لا يطابق الملف الذي تم رفعه.',
+    s3SettingsIncomplete: 'يتطلب محوّل S3 تحديد الحاوية (s3_bucket) والمنطقة (s3_region).',
+    failed: (reason) => `فشل اختبار الاتصال بالتخزين: ${reason}`,
+  },
+  fr: {
+    succeeded: (adapter) => `Le test de connexion au stockage a réussi (adaptateur : ${adapter}).`,
+    downloadMismatch: 'Le fichier de test téléchargé ne correspond pas à celui qui a été envoyé.',
+    s3SettingsIncomplete: 'L’adaptateur S3 nécessite un bucket (s3_bucket) et une région (s3_region).',
+    failed: (reason) => `Le test de connexion au stockage a échoué : ${reason}`,
+  },
+  'pt-BR': {
+    succeeded: (adapter) => `O teste de conexão com o armazenamento foi concluído com sucesso (adaptador: ${adapter}).`,
+    downloadMismatch: 'O arquivo de teste baixado não corresponde ao que foi enviado.',
+    s3SettingsIncomplete: 'O adaptador S3 exige um bucket (s3_bucket) e uma região (s3_region).',
+    failed: (reason) => `O teste de conexão com o armazenamento falhou: ${reason}`,
+  },
+  ru: {
+    succeeded: (adapter) => `Проверка подключения к хранилищу прошла успешно (адаптер: ${adapter}).`,
+    downloadMismatch: 'Скачанный тестовый файл не совпадает с загруженным.',
+    s3SettingsIncomplete: 'Для адаптера S3 нужно указать бакет (s3_bucket) и регион (s3_region).',
+    failed: (reason) => `Проверка подключения к хранилищу не удалась: ${reason}`,
+  },
+  de: {
+    succeeded: (adapter) => `Der Verbindungstest zum Speicher war erfolgreich (Adapter: ${adapter}).`,
+    downloadMismatch: 'Die heruntergeladene Testdatei stimmt nicht mit der hochgeladenen überein.',
+    s3SettingsIncomplete: 'Der S3-Adapter benötigt einen Bucket (s3_bucket) und eine Region (s3_region).',
+    failed: (reason) => `Der Verbindungstest zum Speicher ist fehlgeschlagen: ${reason}`,
+  },
+};
+
+/** Each platform locale table tag → the key that serves it. */
+const KEY_BY_TABLE_TAG: Record<PlatformLocaleTag, StorageTestCopyLocale> = {
+  en: 'en',
+  'zh-Hans': 'zh-CN',
+  'zh-Hant': 'zh-Hant',
+  es: 'es-ES',
+  ar: 'ar',
+  fr: 'fr',
+  'pt-BR': 'pt-BR',
+  ru: 'ru',
+  de: 'de',
+  ja: 'ja-JP',
+  ko: 'ko',
+};
+
+/** The key that serves a caller's code, or `undefined` (⇒ English). */
+export function storageTestCopyLocaleOf(locale: string | undefined): StorageTestCopyLocale | undefined {
+  if (!locale) return undefined;
+  const subtags = locale.split('-');
+  for (let n = subtags.length; n > 0; n -= 1) {
+    const tag = platformLocaleTagOf(subtags.slice(0, n).join('-'));
+    if (tag) return KEY_BY_TABLE_TAG[tag];
+  }
+  return undefined;
+}
+
+/** The copy for a caller's locale; English when the code names no language on the table. */
+export function storageTestCopy(locale: string | undefined): StorageTestCopy {
+  return STORAGE_TEST_COPY[storageTestCopyLocaleOf(locale) ?? 'en'];
+}
diff --git a/packages/services/service-storage/src/storage-test-locale.test.ts b/packages/services/service-storage/src/storage-test-locale.test.ts
new file mode 100644
index 00000000000..5717bc7e994
--- /dev/null
+++ b/packages/services/service-storage/src/storage-test-locale.test.ts
@@ -0,0 +1,211 @@
+// Copyright (c) 2025 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#30335] Setup → Storage → 测试连接 answers in the caller's language.
+ *
+ * The console prints the `storage/test` action's `message` as the toast, bare.
+ * The settings action route hands the handler the caller's display language as
+ * the input's `locale` (`Accept-Language`, else `?locale`), the same source the
+ * mail test notice reads. These pins run the REAL handler the plugin registers,
+ * on a real local adapter, with that input member set or absent.
+ *
+ * `ok`, `severity`, the adapter name and the probe's cleanup are not the
+ * subject: each case asserts the first two are what they were, so a
+ * translation can never have moved a verdict.
+ */
+
+import { describe, expect, it } from 'vitest';
+import { promises as fs } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { StorageServicePlugin } from './storage-service-plugin.js';
+import { LocalStorageAdapter } from './local-storage-adapter.js';
+import { PLATFORM_LOCALE_TAGS } from '@objectstack/spec/system';
+import { storageTestCopy, storageTestCopyLocaleOf, STORAGE_TEST_COPY } from './storage-test-copy.js';
+
+function makeCtx() {
+  const services = new Map<string, unknown>();
+  const hooks: Array<() => Promise<void> | void> = [];
+  const ctx: any = {
+    logger: { info: () => {}, warn: () => {}, error: () => {}, debug: () => {} },
+    registerService: (name: string, svc: unknown) => { services.set(name, svc); },
+    getService: <T>(name: string): T => {
+      const s = services.get(name);
+      if (!s) throw new Error(`service '${name}' not registered`);
+      return s as T;
+    },
+    hook: (event: string, fn: () => Promise<void> | void) => {
+      if (event === 'kernel:ready') hooks.push(fn);
+    },
+    _flushReady: async () => { for (const h of hooks) await h(); },
+  };
+  return ctx;
+}
+
+/** A settings host that keeps the registered action so a test can run it. */
+function makeSettingsHost() {
+  const actions = new Map<string, (input: unknown) => Promise<any>>();
+  return {
+    createClient: (_ns: string) => ({}),
+    getNamespace: async (_ns: string) => ({ values: {} }),
+    subscribe: (_ns: string, _fn: () => void) => {},
+    registerAction: (ns: string, id: string, fn: (input: unknown) => Promise<any>) => {
+      actions.set(`${ns}/${id}`, fn);
+    },
+    run: async (input: Record<string, unknown>) => {
+      const fn = actions.get('storage/test');
+      if (!fn) throw new Error('storage/test was not registered');
+      return await fn({ namespace: 'storage', actionId: 'test', ctx: {}, ...input });
+    },
+  };
+}
+
+async function bootPlugin() {
+  const root = await fs.mkdtemp(join(tmpdir(), 'oss-30335-'));
+  const plugin = new StorageServicePlugin({ adapter: 'local', local: { rootDir: root }, registerRoutes: false });
+  const ctx = makeCtx();
+  const settings = makeSettingsHost();
+  ctx.registerService('settings', settings);
+  await plugin.init(ctx);
+  await plugin.start(ctx);
+  await ctx._flushReady();
+  return { root, settings, plugin };
+}
+
+/** The local adapter with a download that answers bytes other than the ones uploaded. */
+function corruptDownloads(): () => void {
+  const original = LocalStorageAdapter.prototype.download;
+  LocalStorageAdapter.prototype.download = async function (this: LocalStorageAdapter, key: string) {
+    void key;
+    return Buffer.from('not the probe', 'utf-8');
+  } as typeof original;
+  return () => { LocalStorageAdapter.prototype.download = original; };
+}
+
+describe('[#30335] storage/test answers in the caller\'s language', () => {
+  it('zh-CN: the success sentence is Chinese and names the adapter; the verdict is unchanged', async () => {
+    const { root, settings } = await bootPlugin();
+    const result = await settings.run({ values: { adapter: 'local', local_root: root }, locale: 'zh-CN' });
+    expect(result.ok).toBe(true);
+    expect(result.severity).toBe('info');
+    expect(result.message).toBe('存储连接测试成功（适配器：local）。');
+    expect(result.message).not.toContain('round-trip');
+  });
+
+  it('en: the success sentence is the English one the console showed before', async () => {
+    const { root, settings } = await bootPlugin();
+    const result = await settings.run({ values: { adapter: 'local', local_root: root }, locale: 'en-US' });
+    expect(result.ok).toBe(true);
+    expect(result.severity).toBe('info');
+    expect(result.message).toBe('Storage round-trip succeeded (adapter=local).');
+  });
+
+  it('no locale, or one with no copy: English, exactly as an older settings host gets it', async () => {
+    const { root, settings } = await bootPlugin();
+    const values = { adapter: 'local', local_root: root };
+    for (const input of [{ values }, { values, locale: 'tr-TR' }, { values, locale: '' }]) {
+      const result = await settings.run(input);
+      expect(result.ok).toBe(true);
+      expect(result.severity).toBe('info');
+      expect(result.message).toBe('Storage round-trip succeeded (adapter=local).');
+    }
+  });
+
+  it('a language tag without the region still picks its copy (zh → zh-CN)', async () => {
+    const { root, settings } = await bootPlugin();
+    const result = await settings.run({ values: { adapter: 'local', local_root: root }, locale: 'zh' });
+    expect(result.message).toBe('存储连接测试成功（适配器：local）。');
+  });
+
+  it('zh-CN: a download that does not match the upload is refused in Chinese', async () => {
+    const { root, settings } = await bootPlugin();
+    const restore = corruptDownloads();
+    try {
+      const result = await settings.run({ values: { adapter: 'local', local_root: root }, locale: 'zh-CN' });
+      expect(result.ok).toBe(false);
+      expect(result.severity).toBe('error');
+      expect(result.message).toBe('探测文件下载后的内容与上传的不一致。');
+    } finally {
+      restore();
+    }
+    // The probe object is still removed on this path (#13726).
+    const left = await fs.readdir(join(root, '__objectstack_probe__')).catch(() => []);
+    expect(left).toEqual([]);
+  });
+
+  it('zh-CN: incomplete S3 settings are refused in Chinese, naming the two fields', async () => {
+    const { settings } = await bootPlugin();
+    const result = await settings.run({ values: { adapter: 's3', s3_bucket: '', s3_region: '' }, locale: 'zh-CN' });
+    expect(result.ok).toBe(false);
+    expect(result.severity).toBe('error');
+    expect(result.message).toBe('S3 适配器需要填写存储桶（s3_bucket）和区域（s3_region）。');
+  });
+
+  it('no locale: incomplete S3 settings keep the English refusal', async () => {
+    const { settings } = await bootPlugin();
+    const result = await settings.run({ values: { adapter: 's3', s3_bucket: '', s3_region: '' } });
+    expect(result.ok).toBe(false);
+    expect(result.message).toBe('StorageServicePlugin: S3 adapter requires s3_bucket and s3_region');
+  });
+
+  it('zh-CN: the adapter\'s own error text stays verbatim behind a Chinese lead-in', async () => {
+    const { settings } = await bootPlugin();
+    // A root the process cannot create: a path under a regular FILE.
+    const file = join(await fs.mkdtemp(join(tmpdir(), 'oss-30335-file-')), 'not-a-dir');
+    await fs.writeFile(file, 'x');
+    const zh = await settings.run({ values: { adapter: 'local', local_root: join(file, 'root') }, locale: 'zh-CN' });
+    const en = await settings.run({ values: { adapter: 'local', local_root: join(file, 'root') } });
+    expect(zh.ok).toBe(false);
+    expect(zh.severity).toBe('error');
+    expect(en.ok).toBe(false);
+    // English stays the adapter's sentence alone; Chinese is lead-in + that same sentence.
+    expect(en.message.length).toBeGreaterThan(0);
+    expect(zh.message).toBe(`存储连接测试失败：${en.message}`);
+  });
+});
+
+describe('[#30335] the storage/test copy table', () => {
+  const KEYS = ['ar', 'de', 'en', 'es-ES', 'fr', 'ja-JP', 'ko', 'pt-BR', 'ru', 'zh-CN', 'zh-Hant'];
+
+  it('carries all 11 languages of the platform locale table, each with every sentence', () => {
+    expect(Object.keys(STORAGE_TEST_COPY).sort()).toEqual(KEYS);
+    // Every table tag finds its own entry (none falls through to English).
+    expect(PLATFORM_LOCALE_TAGS).toHaveLength(11);
+    for (const tag of PLATFORM_LOCALE_TAGS) {
+      expect(storageTestCopyLocaleOf(tag), tag).toBeDefined();
+    }
+    const en = STORAGE_TEST_COPY.en;
+    for (const key of KEYS) {
+      const copy = STORAGE_TEST_COPY[key as keyof typeof STORAGE_TEST_COPY];
+      expect(Object.keys(copy).sort(), key).toEqual(['downloadMismatch', 'failed', 's3SettingsIncomplete', 'succeeded']);
+      // Placeholders survive verbatim; the two setting keys are named as written.
+      expect(copy.succeeded('ADAPTER_X'), key).toContain('ADAPTER_X');
+      expect(copy.failed('REASON_Y'), key).toContain('REASON_Y');
+      expect(copy.s3SettingsIncomplete, key).toContain('s3_bucket');
+      expect(copy.s3SettingsIncomplete, key).toContain('s3_region');
+      expect(copy.downloadMismatch.length, key).toBeGreaterThan(0);
+      if (key !== 'en') {
+        // A real translation, not the English sentence copied in.
+        expect(copy.succeeded('local'), key).not.toBe(en.succeeded('local'));
+        expect(copy.downloadMismatch, key).not.toBe(en.downloadMismatch);
+        expect(copy.s3SettingsIncomplete, key).not.toBe(en.s3SettingsIncomplete);
+        expect(copy.failed('x'), key).not.toBe(en.failed('x'));
+      }
+    }
+  });
+
+  it('reads a caller\'s code through the platform table: aliases, table tags, then shorter subtags', () => {
+    const cases: Array<[string | undefined, string | undefined]> = [
+      ['zh-CN', 'zh-CN'], ['zh', 'zh-CN'], ['zh-Hans', 'zh-CN'], ['zh-Hans-CN', 'zh-CN'],
+      ['zh-TW', 'zh-Hant'], ['zh-HK', 'zh-Hant'], ['zh-Hant', 'zh-Hant'], ['zh-Hant-TW', 'zh-Hant'],
+      ['ja', 'ja-JP'], ['ja-JP', 'ja-JP'], ['es', 'es-ES'], ['es-MX', 'es-ES'],
+      ['pt', 'pt-BR'], ['pt-BR', 'pt-BR'], ['fr-FR', 'fr'], ['de-DE', 'de'], ['ko-KR', 'ko'],
+      ['ru', 'ru'], ['ar-SA', 'ar'], ['en-US', 'en'], ['EN-gb', 'en'],
+      ['xx-YY', undefined], ['', undefined], [undefined, undefined],
+    ];
+    for (const [code, key] of cases) {
+      expect(storageTestCopyLocaleOf(code), String(code)).toBe(key);
+    }
+    expect(storageTestCopy('xx-YY')).toBe(STORAGE_TEST_COPY.en);
+  });
+});