feat(cli): add /agents slash command to list available agents (#16182)

packages/cli/src/ui/commands/agentsCommand.test.ts

@@ -0,0 +1,85 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { vi, describe, it, expect, beforeEach } from 'vitest';
+import { agentsCommand } from './agentsCommand.js';
+import { createMockCommandContext } from '../../test-utils/mockCommandContext.js';
+import type { Config } from '@google/gemini-cli-core';
+import { MessageType } from '../types.js';
+
+describe('agentsCommand', () => {
+  let mockContext: ReturnType<typeof createMockCommandContext>;
+  let mockConfig: {
+    getAgentRegistry: ReturnType<typeof vi.fn>;
+  };
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+
+    mockConfig = {
+      getAgentRegistry: vi.fn().mockReturnValue({
+        getAllDefinitions: vi.fn().mockReturnValue([]),
+      }),
+    };
+
+    mockContext = createMockCommandContext({
+      services: {
+        config: mockConfig as unknown as Config,
+      },
+    });
+  });
+
+  it('should show an error if config is not available', async () => {
+    const contextWithoutConfig = createMockCommandContext({
+      services: {
+        config: null,
+      },
+    });
+
+    const result = await agentsCommand.action!(contextWithoutConfig, '');
+
+    expect(result).toEqual({
+      type: 'message',
+      messageType: 'error',
+      content: 'Config not loaded.',
+    });
+  });
+
+  it('should show an error if agent registry is not available', async () => {
+    mockConfig.getAgentRegistry = vi.fn().mockReturnValue(undefined);
+
+    const result = await agentsCommand.action!(mockContext, '');
+
+    expect(result).toEqual({
+      type: 'message',
+      messageType: 'error',
+      content: 'Agent registry not found.',
+    });
+  });
+
+  it('should call addItem with correct agents list', async () => {
+    const mockAgents = [
+      {
+        name: 'agent1',
+        displayName: 'Agent One',
+        description: 'desc1',
+        kind: 'local',
+      },
+      { name: 'agent2', description: 'desc2', kind: 'remote' },
+    ];
+    mockConfig.getAgentRegistry().getAllDefinitions.mockReturnValue(mockAgents);
+
+    await agentsCommand.action!(mockContext, '');
+
+    expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+      expect.objectContaining({
+        type: MessageType.AGENTS_LIST,
+        agents: mockAgents,
+      }),
+      expect.any(Number),
+    );
+  });
+});