refactor: move mockI18n

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

frontend/src/test-utils/mock-i18n.ts

@@ -0,0 +1,26 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import type { TFunction } from 'i18next'
+import i18n from 'i18next'
+import { initReactI18next } from 'react-i18next'
+
+/**
+ * Initializes i18n with minimal settings and without any data, so it just returns the used key as translation.
+ *
+ * @return A promise that resolves if i18n has been initialized
+ */
+export const mockI18n = (): Promise<TFunction> => {
+  return i18n.use(initReactI18next).init({
+    lng: 'en',
+    fallbackLng: 'en',
+    ns: ['translationsNS'],
+    defaultNS: 'translationsNS',
+    interpolation: {
+      escapeValue: false
+    },
+    resources: { en: { translationsNS: {} } }
+  })
+}