test: unify i18next mocks into centralized helpers (#30376)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: yyh <yuanyouhuilyz@gmail.com>

web/test/i18n-mock.ts

@@ -0,0 +1,79 @@
+import * as React from 'react'
+import { vi } from 'vitest'
+
+type TranslationMap = Record<string, string | string[]>
+
+/**
+ * Create a t function with optional custom translations
+ * Checks translations[key] first, then translations[ns.key], then returns ns.key as fallback
+ */
+export function createTFunction(translations: TranslationMap, defaultNs?: string) {
+  return (key: string, options?: Record<string, unknown>) => {
+    // Check custom translations first (without namespace)
+    if (translations[key] !== undefined)
+      return translations[key]
+
+    const ns = (options?.ns as string | undefined) ?? defaultNs
+    const fullKey = ns ? `${ns}.${key}` : key
+
+    // Check custom translations with namespace
+    if (translations[fullKey] !== undefined)
+      return translations[fullKey]
+
+    // Serialize params (excluding ns) for test assertions
+    const params = { ...options }
+    delete params.ns
+    const suffix = Object.keys(params).length > 0 ? `:${JSON.stringify(params)}` : ''
+    return `${fullKey}${suffix}`
+  }
+}
+
+/**
+ * Create useTranslation mock with optional custom translations
+ *
+ * @example
+ * vi.mock('react-i18next', () => createUseTranslationMock({
+ *   'operation.confirm': 'Confirm',
+ * }))
+ */
+export function createUseTranslationMock(translations: TranslationMap = {}) {
+  return {
+    useTranslation: (defaultNs?: string) => ({
+      t: createTFunction(translations, defaultNs),
+      i18n: {
+        language: 'en',
+        changeLanguage: vi.fn(),
+      },
+    }),
+  }
+}
+
+/**
+ * Create Trans component mock with optional custom translations
+ */
+export function createTransMock(translations: TranslationMap = {}) {
+  return {
+    Trans: ({ i18nKey, children }: {
+      i18nKey: string
+      children?: React.ReactNode
+    }) => {
+      const text = translations[i18nKey] ?? i18nKey
+      return React.createElement('span', { 'data-i18n-key': i18nKey }, children ?? text)
+    },
+  }
+}
+
+/**
+ * Create complete react-i18next mock (useTranslation + Trans)
+ *
+ * @example
+ * vi.mock('react-i18next', () => createReactI18nextMock({
+ *   'modal.title': 'My Modal',
+ * }))
+ */
+export function createReactI18nextMock(translations: TranslationMap = {}) {
+  return {
+    ...createUseTranslationMock(translations),
+    ...createTransMock(translations),
+  }
+}