[extensions] Add extension management install command (#6703)

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

@@ -0,0 +1,25 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { installCommand } from './install.js';
+import yargs from 'yargs';
+
+describe('extensions install command', () => {
+  it('should fail if no source is provided', () => {
+    const validationParser = yargs([]).command(installCommand).fail(false);
+    expect(() => validationParser.parse('install')).toThrow(
+      'Either a git URL --source or a --path must be provided.',
+    );
+  });
+
+  it('should fail if both git source and local path are provided', () => {
+    const validationParser = yargs([]).command(installCommand).fail(false);
+    expect(() =>
+      validationParser.parse('install --source some-url --path /some/path'),
+    ).toThrow('Arguments source and path are mutually exclusive');
+  });
+});