Test language persistence on localstaorage

packages/i18n/src/init.tsx

@@ -39,7 +39,7 @@ const languageDetectorOptions = {
 const languageDetector = new LanguageDetector(null, languageDetectorOptions);
 const cachedLang = languageDetector.detect();
 
-// register own custom language that returns configured language if no language is cached
+// register custom detector that returns configured language if no language is cached
 if (!cachedLang) {
   languageDetectorOptions.order.push(customLanguageDetectorName);
   const customLanguageDetector = {
@@ -49,7 +49,7 @@ if (!cachedLang) {
     },
   };
   languageDetector.addDetector(customLanguageDetector);
-  languageDetector.detect(); // this will now use our registored detector
+  languageDetector.detect(); // use registered detector
 }
 
 newInstance

packages/i18n/src/tests/init.test.tsx

@@ -3,8 +3,6 @@ import { waitFor, screen, fireEvent, render, cleanup } from '@testing-library/re
 import React from 'react';
 import { useTranslation } from 'react-i18next';
 
-const { OpensrpWebI18nProvider } = module;
-
 afterAll(() => {
   cleanup();
 });
@@ -41,7 +39,23 @@ jest.mock('@opensrp/pkg-config', () => {
   };
 });
 
+const i18nextLngKey = 'i18nextLng';
+let mockStorage = {};
+Object.defineProperty(window, 'localStorage', {
+  value: {
+    setItem: jest.fn((key, value) => (mockStorage[key] = value)),
+    getItem: jest.fn((key) => mockStorage[key]),
+    removeItem: jest.fn((key) => delete mockStorage[key]),
+  },
+});
+
+afterEach(() => {
+  mockStorage = {};
+  cleanup();
+});
+
 test('loads up the correct resources', async () => {
+  const { OpensrpWebI18nProvider } = module;
   const MockComponent = () => {
     const { t, i18n } = useTranslation();
     return (
@@ -72,8 +86,12 @@ test('loads up the correct resources', async () => {
     expect(screen.queryByText(/Jambo/)).not.toBeInTheDocument();
   });
 
+  expect(window.localStorage.getItem(i18nextLngKey)).toBe(undefined);
+
   fireEvent.click(screen.getByText(/change/i));
 
+  // selected language is stored on localstarage
+  expect(window.localStorage.getItem(i18nextLngKey)).toBe('sw_core');
   await waitFor(() => {
     expect(screen.getByText(/Jambo/)).toBeInTheDocument();
     expect(screen.queryByText(/Hello/)).not.toBeInTheDocument();