Improve code coverage for cli package (#13724)

packages/cli/src/core/theme.test.ts

@@ -0,0 +1,54 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { validateTheme } from './theme.js';
+import { themeManager } from '../ui/themes/theme-manager.js';
+import { type LoadedSettings } from '../config/settings.js';
+
+vi.mock('../ui/themes/theme-manager.js', () => ({
+  themeManager: {
+    findThemeByName: vi.fn(),
+  },
+}));
+
+describe('theme', () => {
+  let mockSettings: LoadedSettings;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockSettings = {
+      merged: {
+        ui: {
+          theme: 'test-theme',
+        },
+      },
+    } as unknown as LoadedSettings;
+  });
+
+  it('should return null if theme is found', () => {
+    vi.mocked(themeManager.findThemeByName).mockReturnValue(
+      {} as unknown as ReturnType<typeof themeManager.findThemeByName>,
+    );
+    const result = validateTheme(mockSettings);
+    expect(result).toBeNull();
+    expect(themeManager.findThemeByName).toHaveBeenCalledWith('test-theme');
+  });
+
+  it('should return error message if theme is not found', () => {
+    vi.mocked(themeManager.findThemeByName).mockReturnValue(undefined);
+    const result = validateTheme(mockSettings);
+    expect(result).toBe('Theme "test-theme" not found.');
+    expect(themeManager.findThemeByName).toHaveBeenCalledWith('test-theme');
+  });
+
+  it('should return null if theme is undefined', () => {
+    mockSettings.merged.ui!.theme = undefined;
+    const result = validateTheme(mockSettings);
+    expect(result).toBeNull();
+    expect(themeManager.findThemeByName).not.toHaveBeenCalled();
+  });
+});