Add gemini extensions link command (#7241)

Co-authored-by: Bryan Morgan <bryanmorgan@google.com>

packages/cli/src/commands/extensions/new.test.ts

@@ -0,0 +1,73 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { newCommand } from './new.js';
+import yargs from 'yargs';
+import * as fsPromises from 'node:fs/promises';
+
+vi.mock('node:fs/promises');
+
+const mockedFs = vi.mocked(fsPromises);
+
+describe('extensions new command', () => {
+  beforeEach(() => {
+    vi.resetAllMocks();
+
+    const fakeFiles = [
+      { name: 'context', isDirectory: () => true },
+      { name: 'custom-commands', isDirectory: () => true },
+      { name: 'mcp-server', isDirectory: () => true },
+    ];
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    mockedFs.readdir.mockResolvedValue(fakeFiles as any);
+  });
+
+  it('should fail if no path is provided', async () => {
+    const parser = yargs([]).command(newCommand).fail(false);
+    await expect(parser.parseAsync('new')).rejects.toThrow(
+      'Not enough non-option arguments: got 0, need at least 2',
+    );
+  });
+
+  it('should fail if no template is provided', async () => {
+    const parser = yargs([]).command(newCommand).fail(false);
+    await expect(parser.parseAsync('new /some/path')).rejects.toThrow(
+      'Not enough non-option arguments: got 1, need at least 2',
+    );
+  });
+
+  it('should create directory and copy files when path does not exist', async () => {
+    mockedFs.access.mockRejectedValue(new Error('ENOENT'));
+    mockedFs.mkdir.mockResolvedValue(undefined);
+    mockedFs.cp.mockResolvedValue(undefined);
+
+    const parser = yargs([]).command(newCommand).fail(false);
+
+    await parser.parseAsync('new /some/path context');
+
+    expect(mockedFs.mkdir).toHaveBeenCalledWith('/some/path', {
+      recursive: true,
+    });
+    expect(mockedFs.cp).toHaveBeenCalledWith(
+      expect.stringContaining('context'),
+      '/some/path',
+      { recursive: true },
+    );
+  });
+
+  it('should throw an error if the path already exists', async () => {
+    mockedFs.access.mockResolvedValue(undefined);
+    const parser = yargs([]).command(newCommand).fail(false);
+
+    await expect(parser.parseAsync('new /some/path context')).rejects.toThrow(
+      'Path already exists: /some/path',
+    );
+
+    expect(mockedFs.mkdir).not.toHaveBeenCalled();
+    expect(mockedFs.cp).not.toHaveBeenCalled();
+  });
+});