smoothschedule/frontend/src/hooks/__tests__/useDateFnsLocale.test.ts

import { describe, it, expect, vi, beforeEach } from 'vitest';
import { renderHook } from '@testing-library/react';
import { useDateFnsLocale } from '../useDateFnsLocale';
import { enUS, de, es, fr } from 'date-fns/locale';

// Mock react-i18next
vi.mock('react-i18next', () => ({
  useTranslation: vi.fn(),
}));

import { useTranslation } from 'react-i18next';

describe('useDateFnsLocale', () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  it('returns English locale by default', () => {
    vi.mocked(useTranslation).mockReturnValue({
      i18n: { language: 'en' },
      t: vi.fn(),
      ready: true,
    } as ReturnType<typeof useTranslation>);

    const { result } = renderHook(() => useDateFnsLocale());

    expect(result.current).toBe(enUS);
  });

  it('returns German locale for de', () => {
    vi.mocked(useTranslation).mockReturnValue({
      i18n: { language: 'de' },
      t: vi.fn(),
      ready: true,
    } as ReturnType<typeof useTranslation>);

    const { result } = renderHook(() => useDateFnsLocale());

    expect(result.current).toBe(de);
  });

  it('returns Spanish locale for es', () => {
    vi.mocked(useTranslation).mockReturnValue({
      i18n: { language: 'es' },
      t: vi.fn(),
      ready: true,
    } as ReturnType<typeof useTranslation>);

    const { result } = renderHook(() => useDateFnsLocale());

    expect(result.current).toBe(es);
  });

  it('returns French locale for fr', () => {
    vi.mocked(useTranslation).mockReturnValue({
      i18n: { language: 'fr' },
      t: vi.fn(),
      ready: true,
    } as ReturnType<typeof useTranslation>);

    const { result } = renderHook(() => useDateFnsLocale());

    expect(result.current).toBe(fr);
  });

  it('handles language with region code (en-US)', () => {
    vi.mocked(useTranslation).mockReturnValue({
      i18n: { language: 'en-US' },
      t: vi.fn(),
      ready: true,
    } as ReturnType<typeof useTranslation>);

    const { result } = renderHook(() => useDateFnsLocale());

    expect(result.current).toBe(enUS);
  });

  it('handles language with region code (de-DE)', () => {
    vi.mocked(useTranslation).mockReturnValue({
      i18n: { language: 'de-DE' },
      t: vi.fn(),
      ready: true,
    } as ReturnType<typeof useTranslation>);

    const { result } = renderHook(() => useDateFnsLocale());

    expect(result.current).toBe(de);
  });

  it('returns English locale for unknown language', () => {
    vi.mocked(useTranslation).mockReturnValue({
      i18n: { language: 'xx' },
      t: vi.fn(),
      ready: true,
    } as ReturnType<typeof useTranslation>);

    const { result } = renderHook(() => useDateFnsLocale());

    expect(result.current).toBe(enUS);
  });

  it('returns English locale when language is undefined', () => {
    vi.mocked(useTranslation).mockReturnValue({
      i18n: { language: undefined },
      t: vi.fn(),
      ready: true,
    } as ReturnType<typeof useTranslation>);

    const { result } = renderHook(() => useDateFnsLocale());

    expect(result.current).toBe(enUS);
  });
});