feat: restart MCP servers on /mcp refresh (#5479)

Co-authored-by: Brian Ray <62354532+emeryray2002@users.noreply.github.com>
Co-authored-by: N. Taylor Mullen <ntaylormullen@google.com>

packages/core/src/tools/mcp-client-manager.test.ts

@@ -0,0 +1,54 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { McpClientManager } from './mcp-client-manager.js';
+import { McpClient } from './mcp-client.js';
+import { ToolRegistry } from './tool-registry.js';
+import { PromptRegistry } from '../prompts/prompt-registry.js';
+import { WorkspaceContext } from '../utils/workspaceContext.js';
+
+vi.mock('./mcp-client.js', async () => {
+  const originalModule = await vi.importActual('./mcp-client.js');
+  return {
+    ...originalModule,
+    McpClient: vi.fn(),
+    populateMcpServerCommand: vi.fn(() => ({
+      'test-server': {},
+    })),
+  };
+});
+
+describe('McpClientManager', () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('should discover tools from all servers', async () => {
+    const mockedMcpClient = {
+      connect: vi.fn(),
+      discover: vi.fn(),
+      disconnect: vi.fn(),
+      getStatus: vi.fn(),
+    };
+    vi.mocked(McpClient).mockReturnValue(
+      mockedMcpClient as unknown as McpClient,
+    );
+    const manager = new McpClientManager(
+      {
+        'test-server': {},
+      },
+      '',
+      {} as ToolRegistry,
+      {} as PromptRegistry,
+      false,
+      {} as WorkspaceContext,
+    );
+    await manager.discoverAllMcpTools();
+    expect(mockedMcpClient.connect).toHaveBeenCalledOnce();
+    expect(mockedMcpClient.discover).toHaveBeenCalledOnce();
+  });
+});