additional jest usage

example/test-jest/src/UseTranslationWithInterpolation.js

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+import React from 'react';
+import { useTranslation } from 'react-i18next';
+
+export default function CustomComponent() {
+  const { t } = useTranslation();
+
+  return <div>{t('some.key', { some: 'variable' })}</div>;
+}

example/test-jest/src/UseTranslationWithInterpolation.test.js

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+import React from 'react';
+import { mount } from 'enzyme';
+import UseTranslationWithInterpolation from './UseTranslationWithInterpolation';
+import { useTranslation } from 'react-i18next';
+
+jest.mock('react-i18next', () => ({
+  useTranslation: jest.fn(),
+}));
+
+const tSpy = jest.fn((str) => str);
+const useTranslationSpy = useTranslation;
+
+useTranslationSpy.mockReturnValue({
+  t: tSpy,
+  i18n: {
+    changeLanguage: () => new Promise(() => {}),
+  },
+});
+
+it('test render', () => {
+  const mounted = mount(<UseTranslationWithInterpolation />);
+
+  // console.log(mounted.debug());
+  expect(mounted.contains(<div>some.key</div>)).toBe(true);
+
+  // If you want you can also check how the t function has been called,
+  // but basically this is testing your mock and not the actual code.
+  expect(tSpy).toHaveBeenCalledTimes(1);
+  expect(tSpy).toHaveBeenLastCalledWith('some.key', { some: 'variable' });
+});