[Test Improver] Add unit tests for useI18n composable

shell/composables/useI18n.test.ts

@@ -0,0 +1,122 @@
+describe('useI18n', () => {
+  let useI18nFn: (store: any) => { t: (key: string, args?: unknown, raw?: boolean) => string };
+  let mockStringFor: jest.Mock;
+
+  beforeEach(() => {
+    mockStringFor = jest.fn();
+    jest.resetModules();
+    jest.unmock('@shell/composables/useI18n');
+    jest.mock('@shell/plugins/i18n', () => ({ stringFor: mockStringFor }));
+    useI18nFn = require('@shell/composables/useI18n').useI18n;
+  });
+
+  describe('initialization', () => {
+    it('returns an object with a t function when called with a valid store', () => {
+      const mockStore = { getters: {} };
+      const result = useI18nFn(mockStore);
+
+      expect(typeof result.t).toStrictEqual('function');
+    });
+
+    it.each([
+      {
+        desc:  'null store',
+        store: null,
+      },
+      {
+        desc:  'undefined store',
+        store: undefined,
+      },
+    ])('throws when called with $desc', ({ store }) => {
+      expect(() => useI18nFn(store)).toThrow('usI18n() must be called from setup()');
+    });
+  });
+
+  describe('t()', () => {
+    it('delegates to stringFor with store, key, args, and raw when store is set', () => {
+      const mockStore = { getters: {} };
+
+      mockStringFor.mockReturnValue('translated value');
+
+      const { t } = useI18nFn(mockStore);
+      const result = t('my.translation.key', { count: 5 }, true);
+
+      expect(mockStringFor).toHaveBeenCalledWith(mockStore, 'my.translation.key', { count: 5 }, true);
+      expect(result).toStrictEqual('translated value');
+    });
+
+    it('passes undefined args and raw to stringFor when not supplied', () => {
+      const mockStore = { getters: {} };
+
+      mockStringFor.mockReturnValue('plain');
+
+      const { t } = useI18nFn(mockStore);
+
+      t('plain.key');
+
+      expect(mockStringFor).toHaveBeenCalledWith(mockStore, 'plain.key', undefined, undefined);
+    });
+
+    it('returns the key when store is null after a failed useI18n call', () => {
+      const { t } = useI18nFn({ getters: {} });
+
+      expect(() => useI18nFn(null)).toThrow();
+
+      const result = t('fallback.key');
+
+      expect(mockStringFor).not.toHaveBeenCalled();
+      expect(result).toStrictEqual('fallback.key');
+    });
+
+    it('logs a console warning when store is null and process.env.dev is set', () => {
+      const { t } = useI18nFn({ getters: {} });
+
+      expect(() => useI18nFn(null)).toThrow();
+
+      const warnSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+      const originalDev = process.env.dev;
+
+      process.env.dev = 'true';
+
+      t('some.key');
+
+      expect(warnSpy).toHaveBeenCalledWith('useI18n: store not available');
+
+      process.env.dev = originalDev;
+      warnSpy.mockRestore();
+    });
+
+    it('does not log a warning when store is null and process.env.dev is not set', () => {
+      const { t } = useI18nFn({ getters: {} });
+
+      expect(() => useI18nFn(null)).toThrow();
+
+      const warnSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+      const originalDev = process.env.dev;
+
+      delete process.env.dev;
+
+      t('some.key');
+
+      expect(warnSpy).not.toHaveBeenCalled();
+
+      process.env.dev = originalDev;
+      warnSpy.mockRestore();
+    });
+
+    it('uses the most recently bound store across multiple useI18n calls', () => {
+      const store1 = { id: 'store1' };
+      const store2 = { id: 'store2' };
+
+      mockStringFor.mockReturnValue('ok');
+
+      const { t } = useI18nFn(store1);
+
+      useI18nFn(store2);
+
+      t('key');
+
+      expect(mockStringFor).toHaveBeenCalledWith(store2, 'key', undefined, undefined);
+    });
+  });
+});