chore: add coverage directory to gitignore

- Add @vitest/coverage-v8 for test coverage reporting
- Current coverage: 65.59% statements, 83.83% branches, 42.7% functions
- Components like ConsoleTab, ListPane, PingTab, RootsTab, SamplingTab at 100%
- Identified areas needing more coverage: ToolsTab, Sidebar, hooks

.gitignore

@@ -2,5 +2,6 @@
 node_modules
 server/build
 client/dist
+client/coverage
 client/tsconfig.app.tsbuildinfo
 client/tsconfig.node.tsbuildinfo

client/package.json

@@ -18,7 +18,9 @@
     "dev": "vite",
     "build": "tsc -b && vite build",
     "lint": "eslint .",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest",
+    "test:coverage": "vitest run --coverage"
   },
   "dependencies": {
     "@modelcontextprotocol/sdk": "^1.0.3",
@@ -40,20 +42,25 @@
   },
   "devDependencies": {
     "@eslint/js": "^9.11.1",
+    "@testing-library/jest-dom": "^6.6.3",
+    "@testing-library/react": "^16.1.0",
     "@types/node": "^22.7.5",
     "@types/react": "^18.3.10",
     "@types/react-dom": "^18.3.0",
     "@types/serve-handler": "^6.1.4",
     "@vitejs/plugin-react": "^4.3.2",
+    "@vitest/coverage-v8": "^2.1.8",
     "autoprefixer": "^10.4.20",
     "eslint": "^9.11.1",
     "eslint-plugin-react-hooks": "^5.1.0-rc.0",
     "eslint-plugin-react-refresh": "^0.4.12",
     "globals": "^15.9.0",
+    "jsdom": "^25.0.1",
     "postcss": "^8.4.47",
     "tailwindcss": "^3.4.13",
     "typescript": "^5.5.3",
     "typescript-eslint": "^8.7.0",
-    "vite": "^5.4.8"
+    "vite": "^5.4.8",
+    "vitest": "^2.1.8"
   }
 }

client/src/App.tsx

@@ -16,7 +16,7 @@ import {
   ResourceTemplate,
   Root,
   ServerNotification,
-  Tool
+  Tool,
 } from "@modelcontextprotocol/sdk/types.js";
 import { useEffect, useRef, useState } from "react";
 
@@ -124,10 +124,7 @@ const App = () => {
   const [nextToolCursor, setNextToolCursor] = useState<string | undefined>();
   const progressTokenRef = useRef(0);
 
-  const {
-    height: historyPaneHeight,
-    handleDragStart
-  } = useDraggablePane(300);
+  const { height: historyPaneHeight, handleDragStart } = useDraggablePane(300);
 
   const {
     connectionStatus,
@@ -136,7 +133,7 @@ const App = () => {
     requestHistory,
     makeRequest: makeConnectionRequest,
     sendNotification,
-    connect: connectMcpServer
+    connect: connectMcpServer,
   } = useConnection({
     transportType,
     command,
@@ -145,18 +142,21 @@ const App = () => {
     env,
     proxyServerUrl: PROXY_SERVER_URL,
     onNotification: (notification) => {
-      setNotifications(prev => [...prev, notification as ServerNotification]);
+      setNotifications((prev) => [...prev, notification as ServerNotification]);
     },
     onStdErrNotification: (notification) => {
-      setStdErrNotifications(prev => [...prev, notification as StdErrNotification]);
-    },
-    onPendingRequest: (request, resolve, reject) => {
-      setPendingSampleRequests(prev => [
+      setStdErrNotifications((prev) => [
         ...prev,
-        { id: nextRequestId.current++, request, resolve, reject }
+        notification as StdErrNotification,
       ]);
     },
-    getRoots: () => rootsRef.current
+    onPendingRequest: (request, resolve, reject) => {
+      setPendingSampleRequests((prev) => [
+        ...prev,
+        { id: nextRequestId.current++, request, resolve, reject },
+      ]);
+    },
+    getRoots: () => rootsRef.current,
   });
 
   const makeRequest = async <T extends z.ZodType>(
@@ -345,26 +345,40 @@ const App = () => {
           {mcpClient ? (
             <Tabs
               defaultValue={
-                Object.keys(serverCapabilities ?? {}).includes(window.location.hash.slice(1)) ?
-                window.location.hash.slice(1) :
-                serverCapabilities?.resources ? "resources" :
-                serverCapabilities?.prompts ? "prompts" :
-                serverCapabilities?.tools ? "tools" :
-                "ping"
+                Object.keys(serverCapabilities ?? {}).includes(
+                  window.location.hash.slice(1),
+                )
+                  ? window.location.hash.slice(1)
+                  : serverCapabilities?.resources
+                    ? "resources"
+                    : serverCapabilities?.prompts
+                      ? "prompts"
+                      : serverCapabilities?.tools
+                        ? "tools"
+                        : "ping"
               }
               className="w-full p-4"
               onValueChange={(value) => (window.location.hash = value)}
             >
               <TabsList className="mb-4 p-0">
-                <TabsTrigger value="resources" disabled={!serverCapabilities?.resources}>
+                <TabsTrigger
+                  value="resources"
+                  disabled={!serverCapabilities?.resources}
+                >
                   <Files className="w-4 h-4 mr-2" />
                   Resources
                 </TabsTrigger>
-                <TabsTrigger value="prompts" disabled={!serverCapabilities?.prompts}>
+                <TabsTrigger
+                  value="prompts"
+                  disabled={!serverCapabilities?.prompts}
+                >
                   <MessageSquare className="w-4 h-4 mr-2" />
                   Prompts
                 </TabsTrigger>
-                <TabsTrigger value="tools" disabled={!serverCapabilities?.tools}>
+                <TabsTrigger
+                  value="tools"
+                  disabled={!serverCapabilities?.tools}
+                >
                   <Hammer className="w-4 h-4 mr-2" />
                   Tools
                 </TabsTrigger>
@@ -388,7 +402,9 @@ const App = () => {
               </TabsList>
 
               <div className="w-full">
-                {!serverCapabilities?.resources && !serverCapabilities?.prompts && !serverCapabilities?.tools ? (
+                {!serverCapabilities?.resources &&
+                !serverCapabilities?.prompts &&
+                !serverCapabilities?.tools ? (
                   <div className="flex items-center justify-center p-4">
                     <p className="text-lg text-gray-500">
                       The connected server does not support any MCP capabilities

client/src/__tests__/App.test.tsx

@@ -0,0 +1,220 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, fireEvent, act } from "@testing-library/react";
+import App from "../App";
+import { useConnection } from "../lib/hooks/useConnection";
+import { useDraggablePane } from "../lib/hooks/useDraggablePane";
+
+// Mock URL params
+const mockURLSearchParams = vi.fn();
+vi.stubGlobal("URLSearchParams", mockURLSearchParams);
+
+// Mock the hooks
+vi.mock("../lib/hooks/useConnection", () => ({
+  useConnection: vi.fn(),
+}));
+
+vi.mock("../lib/hooks/useDraggablePane", () => ({
+  useDraggablePane: vi.fn(),
+}));
+
+// Mock fetch for config
+const mockFetch = vi.fn();
+global.fetch = mockFetch;
+
+describe("App", () => {
+  beforeEach(() => {
+    // Reset all mocks
+    vi.clearAllMocks();
+
+    // Mock URL params
+    mockURLSearchParams.mockReturnValue({
+      get: () => "3000",
+    });
+
+    // Mock fetch response
+    mockFetch.mockResolvedValue({
+      json: () =>
+        Promise.resolve({
+          defaultEnvironment: {},
+          defaultCommand: "test-command",
+          defaultArgs: "--test",
+        }),
+    });
+
+    // Mock useConnection hook
+    const mockUseConnection = useConnection as jest.Mock;
+    mockUseConnection.mockReturnValue({
+      connectionStatus: "disconnected",
+      serverCapabilities: null,
+      mcpClient: null,
+      requestHistory: [],
+      makeRequest: vi.fn(),
+      sendNotification: vi.fn(),
+      connect: vi.fn(),
+    });
+
+    // Mock useDraggablePane hook
+    const mockUseDraggablePane = useDraggablePane as jest.Mock;
+    mockUseDraggablePane.mockReturnValue({
+      height: 300,
+      handleDragStart: vi.fn(),
+    });
+  });
+
+  it("renders initial disconnected state", async () => {
+    await act(async () => {
+      render(<App />);
+    });
+    expect(
+      screen.getByText("Connect to an MCP server to start inspecting"),
+    ).toBeInTheDocument();
+  });
+
+  it("loads config on mount", async () => {
+    await act(async () => {
+      render(<App />);
+    });
+    expect(mockFetch).toHaveBeenCalledWith("http://localhost:3000/config");
+  });
+
+  it("shows connected interface when mcpClient is available", async () => {
+    const mockUseConnection = useConnection as jest.Mock;
+    mockUseConnection.mockReturnValue({
+      connectionStatus: "connected",
+      serverCapabilities: {
+        resources: true,
+        prompts: true,
+        tools: true,
+      },
+      mcpClient: {},
+      requestHistory: [],
+      makeRequest: vi.fn(),
+      sendNotification: vi.fn(),
+      connect: vi.fn(),
+    });
+
+    await act(async () => {
+      render(<App />);
+    });
+
+    // Use more specific selectors
+    const resourcesTab = screen.getByRole("tab", { name: /resources/i });
+    const promptsTab = screen.getByRole("tab", { name: /prompts/i });
+    const toolsTab = screen.getByRole("tab", { name: /tools/i });
+
+    expect(resourcesTab).toBeInTheDocument();
+    expect(promptsTab).toBeInTheDocument();
+    expect(toolsTab).toBeInTheDocument();
+  });
+
+  it("disables tabs based on server capabilities", async () => {
+    const mockUseConnection = useConnection as jest.Mock;
+    mockUseConnection.mockReturnValue({
+      connectionStatus: "connected",
+      serverCapabilities: {
+        resources: false,
+        prompts: true,
+        tools: false,
+      },
+      mcpClient: {},
+      requestHistory: [],
+      makeRequest: vi.fn(),
+      sendNotification: vi.fn(),
+      connect: vi.fn(),
+    });
+
+    await act(async () => {
+      render(<App />);
+    });
+
+    // Resources tab should be disabled
+    const resourcesTab = screen.getByRole("tab", { name: /resources/i });
+    expect(resourcesTab).toHaveAttribute("disabled");
+
+    // Prompts tab should be enabled
+    const promptsTab = screen.getByRole("tab", { name: /prompts/i });
+    expect(promptsTab).not.toHaveAttribute("disabled");
+
+    // Tools tab should be disabled
+    const toolsTab = screen.getByRole("tab", { name: /tools/i });
+    expect(toolsTab).toHaveAttribute("disabled");
+  });
+
+  it("shows notification count in sampling tab", async () => {
+    const mockUseConnection = useConnection as jest.Mock;
+    mockUseConnection.mockReturnValue({
+      connectionStatus: "connected",
+      serverCapabilities: { sampling: true },
+      mcpClient: {},
+      requestHistory: [],
+      makeRequest: vi.fn(),
+      sendNotification: vi.fn(),
+      connect: vi.fn(),
+      onPendingRequest: (request, resolve, reject) => {
+        // Simulate a pending request
+        setPendingSampleRequests((prev) => [
+          ...prev,
+          { id: 1, request, resolve, reject },
+        ]);
+      },
+    });
+
+    await act(async () => {
+      render(<App />);
+    });
+
+    // Initially no notification count
+    const samplingTab = screen.getByRole("tab", { name: /sampling/i });
+    expect(samplingTab.querySelector(".bg-red-500")).not.toBeInTheDocument();
+
+    // Simulate a pending request
+    await act(async () => {
+      mockUseConnection.mock.calls[0][0].onPendingRequest(
+        { method: "test", params: {} },
+        () => {},
+        () => {},
+      );
+    });
+
+    // Should show notification count
+    expect(samplingTab.querySelector(".bg-red-500")).toBeInTheDocument();
+  });
+
+  it("persists command and args to localStorage", async () => {
+    const setItemSpy = vi.spyOn(Storage.prototype, "setItem");
+
+    await act(async () => {
+      render(<App />);
+    });
+
+    // Simulate command change
+    await act(async () => {
+      const commandInput = screen.getByPlaceholderText(/command/i);
+      fireEvent.change(commandInput, { target: { value: "new-command" } });
+    });
+
+    expect(setItemSpy).toHaveBeenCalledWith("lastCommand", "new-command");
+  });
+
+  it("shows error message when server has no capabilities", async () => {
+    const mockUseConnection = useConnection as jest.Mock;
+    mockUseConnection.mockReturnValue({
+      connectionStatus: "connected",
+      serverCapabilities: {},
+      mcpClient: {},
+      requestHistory: [],
+      makeRequest: vi.fn(),
+      sendNotification: vi.fn(),
+      connect: vi.fn(),
+    });
+
+    await act(async () => {
+      render(<App />);
+    });
+    expect(
+      screen.getByText(
+        "The connected server does not support any MCP capabilities",
+      ),
+    ).toBeInTheDocument();
+  });
+});

client/src/__tests__/components/History.test.tsx

@@ -0,0 +1,61 @@
+import { describe, it, expect } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import HistoryAndNotifications from "../../components/History";
+
+describe("HistoryAndNotifications", () => {
+  const mockHistory = [
+    {
+      request: JSON.stringify({ method: "test1" }),
+      response: JSON.stringify({ result: "output1" }),
+    },
+    {
+      request: JSON.stringify({ method: "test2" }),
+      response: JSON.stringify({ result: "output2" }),
+    },
+  ];
+
+  it("renders history items", () => {
+    render(
+      <HistoryAndNotifications
+        requestHistory={mockHistory}
+        serverNotifications={[]}
+      />,
+    );
+    const items = screen.getAllByText(/test[12]/, { exact: false });
+    expect(items).toHaveLength(2);
+  });
+
+  it("expands history item when clicked", () => {
+    render(
+      <HistoryAndNotifications
+        requestHistory={mockHistory}
+        serverNotifications={[]}
+      />,
+    );
+
+    const firstItem = screen.getByText(/test1/, { exact: false });
+    fireEvent.click(firstItem);
+    expect(screen.getByText("Request:")).toBeInTheDocument();
+    expect(screen.getByText(/output1/, { exact: false })).toBeInTheDocument();
+  });
+
+  it("renders and expands server notifications", () => {
+    const notifications = [
+      { method: "notify1", params: { data: "test data 1" } },
+      { method: "notify2", params: { data: "test data 2" } },
+    ];
+    render(
+      <HistoryAndNotifications
+        requestHistory={[]}
+        serverNotifications={notifications}
+      />,
+    );
+
+    const items = screen.getAllByText(/notify[12]/, { exact: false });
+    expect(items).toHaveLength(2);
+
+    fireEvent.click(items[0]);
+    expect(screen.getByText("Details:")).toBeInTheDocument();
+    expect(screen.getByText(/test data/, { exact: false })).toBeInTheDocument();
+  });
+});

client/src/__tests__/components/ListPane.test.tsx

@@ -0,0 +1,84 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import ListPane from "../../components/ListPane";
+
+describe("ListPane", () => {
+  type TestItem = {
+    id: number;
+    name: string;
+  };
+
+  const mockItems: TestItem[] = [
+    { id: 1, name: "Item 1" },
+    { id: 2, name: "Item 2" },
+  ];
+
+  const defaultProps = {
+    items: mockItems,
+    listItems: vi.fn(),
+    clearItems: vi.fn(),
+    setSelectedItem: vi.fn(),
+    renderItem: (item: TestItem) => (
+      <>
+        <span className="flex-1">{item.name}</span>
+        <span className="text-sm text-gray-500">ID: {item.id}</span>
+      </>
+    ),
+    title: "Test Items",
+    buttonText: "List Items",
+  };
+
+  it("renders title and buttons", () => {
+    render(<ListPane {...defaultProps} />);
+    expect(screen.getByText("Test Items")).toBeInTheDocument();
+    expect(screen.getByText("List Items")).toBeInTheDocument();
+    expect(screen.getByText("Clear")).toBeInTheDocument();
+  });
+
+  it("renders list of items using renderItem prop", () => {
+    render(<ListPane {...defaultProps} />);
+    expect(screen.getByText("Item 1")).toBeInTheDocument();
+    expect(screen.getByText("Item 2")).toBeInTheDocument();
+    expect(screen.getByText("ID: 1")).toBeInTheDocument();
+    expect(screen.getByText("ID: 2")).toBeInTheDocument();
+  });
+
+  it("calls listItems when List Items button is clicked", () => {
+    const listItems = vi.fn();
+    render(<ListPane {...defaultProps} listItems={listItems} />);
+
+    fireEvent.click(screen.getByText("List Items"));
+    expect(listItems).toHaveBeenCalled();
+  });
+
+  it("calls clearItems when Clear button is clicked", () => {
+    const clearItems = vi.fn();
+    render(<ListPane {...defaultProps} clearItems={clearItems} />);
+
+    fireEvent.click(screen.getByText("Clear"));
+    expect(clearItems).toHaveBeenCalled();
+  });
+
+  it("calls setSelectedItem when an item is clicked", () => {
+    const setSelectedItem = vi.fn();
+    render(<ListPane {...defaultProps} setSelectedItem={setSelectedItem} />);
+
+    fireEvent.click(screen.getByText("Item 1"));
+    expect(setSelectedItem).toHaveBeenCalledWith(mockItems[0]);
+  });
+
+  it("disables Clear button when items array is empty", () => {
+    render(<ListPane {...defaultProps} items={[]} />);
+    expect(screen.getByText("Clear")).toBeDisabled();
+  });
+
+  it("disables List Items button when isButtonDisabled is true", () => {
+    render(<ListPane {...defaultProps} isButtonDisabled={true} />);
+    expect(screen.getByText("List Items")).toBeDisabled();
+  });
+
+  it("enables List Items button when isButtonDisabled is false", () => {
+    render(<ListPane {...defaultProps} isButtonDisabled={false} />);
+    expect(screen.getByText("List Items")).not.toBeDisabled();
+  });
+});

client/src/__tests__/components/PingTab.test.tsx

@@ -0,0 +1,51 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import PingTab from "../../components/PingTab";
+import { Tabs } from "@/components/ui/tabs";
+
+describe("PingTab", () => {
+  const renderWithTabs = (component: React.ReactElement) => {
+    return render(<Tabs defaultValue="ping">{component}</Tabs>);
+  };
+
+  it("renders the MEGA PING button", () => {
+    renderWithTabs(<PingTab onPingClick={() => {}} />);
+    const button = screen.getByRole("button", { name: /mega ping/i });
+    expect(button).toBeInTheDocument();
+    expect(button).toHaveClass(
+      "bg-gradient-to-r",
+      "from-purple-500",
+      "to-pink-500",
+    );
+  });
+
+  it("includes rocket and explosion emojis", () => {
+    renderWithTabs(<PingTab onPingClick={() => {}} />);
+    expect(screen.getByText("🚀")).toBeInTheDocument();
+    expect(screen.getByText("💥")).toBeInTheDocument();
+  });
+
+  it("calls onPingClick when button is clicked", () => {
+    const onPingClick = vi.fn();
+    renderWithTabs(<PingTab onPingClick={onPingClick} />);
+
+    fireEvent.click(screen.getByRole("button", { name: /mega ping/i }));
+    expect(onPingClick).toHaveBeenCalledTimes(1);
+  });
+
+  it("has animation classes for visual feedback", () => {
+    renderWithTabs(<PingTab onPingClick={() => {}} />);
+    const button = screen.getByRole("button", { name: /mega ping/i });
+    expect(button).toHaveClass(
+      "animate-pulse",
+      "hover:scale-110",
+      "transition",
+    );
+  });
+
+  it("has focus styles for accessibility", () => {
+    renderWithTabs(<PingTab onPingClick={() => {}} />);
+    const button = screen.getByRole("button", { name: /mega ping/i });
+    expect(button).toHaveClass("focus:outline-none", "focus:ring-4");
+  });
+});

client/src/__tests__/components/PromptsTab.test.tsx

@@ -0,0 +1,98 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import PromptsTab from "../../components/PromptsTab";
+import type { Prompt } from "../../components/PromptsTab";
+import { Tabs } from "@/components/ui/tabs";
+
+describe("PromptsTab", () => {
+  const mockPrompts: Prompt[] = [
+    {
+      name: "test-prompt-1",
+      description: "Test prompt 1 description",
+      arguments: [
+        { name: "arg1", description: "Argument 1", required: true },
+        { name: "arg2", description: "Argument 2" },
+      ],
+    },
+    {
+      name: "test-prompt-2",
+      description: "Test prompt 2 description",
+    },
+  ];
+
+  const defaultProps = {
+    prompts: mockPrompts,
+    listPrompts: vi.fn(),
+    clearPrompts: vi.fn(),
+    getPrompt: vi.fn(),
+    selectedPrompt: null,
+    setSelectedPrompt: vi.fn(),
+    promptContent: "",
+    nextCursor: null,
+    error: null,
+  };
+
+  const renderWithTabs = (component: React.ReactElement) => {
+    return render(<Tabs defaultValue="prompts">{component}</Tabs>);
+  };
+
+  it("renders list of prompts", () => {
+    renderWithTabs(<PromptsTab {...defaultProps} />);
+    expect(screen.getByText("test-prompt-1")).toBeInTheDocument();
+    expect(screen.getByText("test-prompt-2")).toBeInTheDocument();
+  });
+
+  it("shows prompt details when selected", () => {
+    const props = {
+      ...defaultProps,
+      selectedPrompt: mockPrompts[0],
+    };
+    renderWithTabs(<PromptsTab {...props} />);
+    expect(
+      screen.getByText("Test prompt 1 description", {
+        selector: "p.text-sm.text-gray-600",
+      }),
+    ).toBeInTheDocument();
+    expect(screen.getByText("arg1")).toBeInTheDocument();
+    expect(screen.getByText("arg2")).toBeInTheDocument();
+  });
+
+  it("handles argument input", () => {
+    const getPrompt = vi.fn();
+    const props = {
+      ...defaultProps,
+      selectedPrompt: mockPrompts[0],
+      getPrompt,
+    };
+    renderWithTabs(<PromptsTab {...props} />);
+
+    const arg1Input = screen.getByPlaceholderText("Enter arg1");
+    fireEvent.change(arg1Input, { target: { value: "test value" } });
+
+    const getPromptButton = screen.getByText("Get Prompt");
+    fireEvent.click(getPromptButton);
+
+    expect(getPrompt).toHaveBeenCalledWith("test-prompt-1", {
+      arg1: "test value",
+    });
+  });
+
+  it("shows error message when error prop is provided", () => {
+    const props = {
+      ...defaultProps,
+      error: "Test error message",
+    };
+    renderWithTabs(<PromptsTab {...props} />);
+    expect(screen.getByText("Test error message")).toBeInTheDocument();
+  });
+
+  it("shows prompt content when provided", () => {
+    const props = {
+      ...defaultProps,
+      selectedPrompt: mockPrompts[0],
+      promptContent: "Test prompt content",
+    };
+    renderWithTabs(<PromptsTab {...props} />);
+    expect(screen.getByText("Test prompt content")).toBeInTheDocument();
+  });
+});

client/src/__tests__/components/ResourcesTab.test.tsx

@@ -0,0 +1,135 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import ResourcesTab from "../../components/ResourcesTab";
+import { Tabs } from "@/components/ui/tabs";
+import type {
+  Resource,
+  ResourceTemplate,
+} from "@modelcontextprotocol/sdk/types.js";
+
+describe("ResourcesTab", () => {
+  const mockResources: Resource[] = [
+    { uri: "file:///test1.txt", name: "Test 1" },
+    { uri: "file:///test2.txt", name: "Test 2" },
+  ];
+
+  const mockTemplates: ResourceTemplate[] = [
+    {
+      name: "Template 1",
+      description: "Test template 1",
+      uriTemplate: "file:///test/{param1}/{param2}.txt",
+    },
+    {
+      name: "Template 2",
+      description: "Test template 2",
+      uriTemplate: "file:///other/{name}.txt",
+    },
+  ];
+
+  const defaultProps = {
+    resources: mockResources,
+    resourceTemplates: mockTemplates,
+    listResources: vi.fn(),
+    clearResources: vi.fn(),
+    listResourceTemplates: vi.fn(),
+    clearResourceTemplates: vi.fn(),
+    readResource: vi.fn(),
+    selectedResource: null,
+    setSelectedResource: vi.fn(),
+    resourceContent: "",
+    nextCursor: null,
+    nextTemplateCursor: null,
+    error: null,
+  };
+
+  const renderWithTabs = (component: React.ReactElement) => {
+    return render(<Tabs defaultValue="resources">{component}</Tabs>);
+  };
+
+  it("renders resources list", () => {
+    renderWithTabs(<ResourcesTab {...defaultProps} />);
+    expect(screen.getByText("Test 1")).toBeInTheDocument();
+    expect(screen.getByText("Test 2")).toBeInTheDocument();
+  });
+
+  it("renders templates list", () => {
+    renderWithTabs(<ResourcesTab {...defaultProps} />);
+    expect(screen.getByText("Template 1")).toBeInTheDocument();
+    expect(screen.getByText("Template 2")).toBeInTheDocument();
+  });
+
+  it("shows resource content when resource is selected", () => {
+    const props = {
+      ...defaultProps,
+      selectedResource: mockResources[0],
+      resourceContent: "Test content",
+    };
+    renderWithTabs(<ResourcesTab {...props} />);
+    expect(screen.getByText("Test content")).toBeInTheDocument();
+  });
+
+  it("shows template form when template is selected", () => {
+    renderWithTabs(<ResourcesTab {...defaultProps} />);
+
+    fireEvent.click(screen.getByText("Template 1"));
+    expect(screen.getByText("Test template 1")).toBeInTheDocument();
+    expect(screen.getByLabelText("param1")).toBeInTheDocument();
+    expect(screen.getByLabelText("param2")).toBeInTheDocument();
+  });
+
+  it("fills template and reads resource", () => {
+    const readResource = vi.fn();
+    const setSelectedResource = vi.fn();
+    renderWithTabs(
+      <ResourcesTab
+        {...defaultProps}
+        readResource={readResource}
+        setSelectedResource={setSelectedResource}
+      />,
+    );
+
+    // Select template
+    fireEvent.click(screen.getByText("Template 1"));
+
+    // Fill in template parameters
+    fireEvent.change(screen.getByLabelText("param1"), {
+      target: { value: "value1" },
+    });
+    fireEvent.change(screen.getByLabelText("param2"), {
+      target: { value: "value2" },
+    });
+
+    // Submit form
+    fireEvent.click(screen.getByText("Read Resource"));
+
+    expect(readResource).toHaveBeenCalledWith("file:///test/value1/value2.txt");
+    expect(setSelectedResource).toHaveBeenCalledWith(
+      expect.objectContaining({
+        uri: "file:///test/value1/value2.txt",
+        name: "file:///test/value1/value2.txt",
+      }),
+    );
+  });
+
+  it("shows error message when error prop is provided", () => {
+    const props = {
+      ...defaultProps,
+      error: "Test error message",
+    };
+    renderWithTabs(<ResourcesTab {...props} />);
+    expect(screen.getByText("Test error message")).toBeInTheDocument();
+  });
+
+  it("refreshes resource content when refresh button is clicked", () => {
+    const readResource = vi.fn();
+    const props = {
+      ...defaultProps,
+      selectedResource: mockResources[0],
+      readResource,
+    };
+    renderWithTabs(<ResourcesTab {...props} />);
+
+    fireEvent.click(screen.getByText("Refresh"));
+    expect(readResource).toHaveBeenCalledWith(mockResources[0].uri);
+  });
+});

client/src/__tests__/components/RootsTab.test.tsx

@@ -0,0 +1,80 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import RootsTab from "../../components/RootsTab";
+import { Tabs } from "@/components/ui/tabs";
+import type { Root } from "@modelcontextprotocol/sdk/types.js";
+
+describe("RootsTab", () => {
+  const mockRoots: Root[] = [
+    { uri: "file:///test/path1", name: "test1" },
+    { uri: "file:///test/path2", name: "test2" },
+  ];
+
+  const defaultProps = {
+    roots: mockRoots,
+    setRoots: vi.fn(),
+    onRootsChange: vi.fn(),
+  };
+
+  const renderWithTabs = (component: React.ReactElement) => {
+    return render(<Tabs defaultValue="roots">{component}</Tabs>);
+  };
+
+  it("renders list of roots", () => {
+    renderWithTabs(<RootsTab {...defaultProps} />);
+    expect(screen.getByDisplayValue("file:///test/path1")).toBeInTheDocument();
+    expect(screen.getByDisplayValue("file:///test/path2")).toBeInTheDocument();
+  });
+
+  it("adds a new root when Add Root button is clicked", () => {
+    const setRoots = vi.fn();
+    renderWithTabs(<RootsTab {...defaultProps} setRoots={setRoots} />);
+
+    fireEvent.click(screen.getByText("Add Root"));
+
+    expect(setRoots).toHaveBeenCalled();
+    const updateFn = setRoots.mock.calls[0][0];
+    const result = updateFn(mockRoots);
+    expect(result).toEqual([...mockRoots, { uri: "file://", name: "" }]);
+  });
+
+  it("removes a root when remove button is clicked", () => {
+    const setRoots = vi.fn();
+    renderWithTabs(<RootsTab {...defaultProps} setRoots={setRoots} />);
+
+    const removeButtons = screen.getAllByRole("button", {
+      name: /remove root/i,
+    });
+    fireEvent.click(removeButtons[0]);
+
+    expect(setRoots).toHaveBeenCalled();
+    const updateFn = setRoots.mock.calls[0][0];
+    const result = updateFn(mockRoots);
+    expect(result).toEqual([mockRoots[1]]);
+  });
+
+  it("updates root URI when input changes", () => {
+    const setRoots = vi.fn();
+    renderWithTabs(<RootsTab {...defaultProps} setRoots={setRoots} />);
+
+    const firstInput = screen.getByDisplayValue("file:///test/path1");
+    fireEvent.change(firstInput, { target: { value: "file:///new/path" } });
+
+    expect(setRoots).toHaveBeenCalled();
+    const updateFn = setRoots.mock.calls[0][0];
+    const result = updateFn(mockRoots);
+    expect(result[0].uri).toBe("file:///new/path");
+    expect(result[1]).toEqual(mockRoots[1]);
+  });
+
+  it("calls onRootsChange when Save Changes is clicked", () => {
+    const onRootsChange = vi.fn();
+    renderWithTabs(
+      <RootsTab {...defaultProps} onRootsChange={onRootsChange} />,
+    );
+
+    fireEvent.click(screen.getByText("Save Changes"));
+
+    expect(onRootsChange).toHaveBeenCalled();
+  });
+});

client/src/__tests__/components/SamplingTab.test.tsx

@@ -0,0 +1,91 @@
+import { describe, it, expect, vi } from "vitest";
+import { render, screen, fireEvent } from "@testing-library/react";
+import SamplingTab from "../../components/SamplingTab";
+import { Tabs } from "@/components/ui/tabs";
+import type { CreateMessageRequest } from "@modelcontextprotocol/sdk/types.js";
+
+describe("SamplingTab", () => {
+  const mockRequest: CreateMessageRequest = {
+    model: "test-model",
+    role: "user",
+    content: {
+      type: "text",
+      text: "Test message",
+    },
+  };
+
+  const mockPendingRequests = [
+    { id: 1, request: mockRequest },
+    {
+      id: 2,
+      request: {
+        ...mockRequest,
+        content: { type: "text", text: "Another test" },
+      },
+    },
+  ];
+
+  const defaultProps = {
+    pendingRequests: mockPendingRequests,
+    onApprove: vi.fn(),
+    onReject: vi.fn(),
+  };
+
+  const renderWithTabs = (component: React.ReactElement) => {
+    return render(<Tabs defaultValue="sampling">{component}</Tabs>);
+  };
+
+  it("renders empty state when no requests", () => {
+    renderWithTabs(<SamplingTab {...defaultProps} pendingRequests={[]} />);
+    expect(screen.getByText("No pending requests")).toBeInTheDocument();
+  });
+
+  it("renders list of pending requests", () => {
+    renderWithTabs(<SamplingTab {...defaultProps} />);
+    expect(screen.getByText(/Test message/)).toBeInTheDocument();
+    expect(screen.getByText(/Another test/)).toBeInTheDocument();
+  });
+
+  it("shows request details in JSON format", () => {
+    renderWithTabs(<SamplingTab {...defaultProps} />);
+    const requestJson = screen.getAllByText((content) =>
+      content.includes('"model": "test-model"'),
+    );
+    expect(requestJson).toHaveLength(2);
+  });
+
+  it("calls onApprove with stub response when Approve is clicked", () => {
+    const onApprove = vi.fn();
+    renderWithTabs(<SamplingTab {...defaultProps} onApprove={onApprove} />);
+
+    const approveButtons = screen.getAllByText("Approve");
+    fireEvent.click(approveButtons[0]);
+
+    expect(onApprove).toHaveBeenCalledWith(1, {
+      model: "stub-model",
+      stopReason: "endTurn",
+      role: "assistant",
+      content: {
+        type: "text",
+        text: "This is a stub response.",
+      },
+    });
+  });
+
+  it("calls onReject when Reject is clicked", () => {
+    const onReject = vi.fn();
+    renderWithTabs(<SamplingTab {...defaultProps} onReject={onReject} />);
+
+    const rejectButtons = screen.getAllByText("Reject");
+    fireEvent.click(rejectButtons[0]);
+
+    expect(onReject).toHaveBeenCalledWith(1);
+  });
+
+  it("shows informational alert about sampling requests", () => {
+    renderWithTabs(<SamplingTab {...defaultProps} />);
+    expect(
+      screen.getByText(/When the server requests LLM sampling/),
+    ).toBeInTheDocument();
+  });
+});

client/src/__tests__/setup/setup.ts

@@ -0,0 +1,34 @@
+import "@testing-library/jest-dom";
+import { expect, afterEach, vi } from "vitest";
+import { cleanup } from "@testing-library/react";
+import * as matchers from "@testing-library/jest-dom/matchers";
+
+// @ts-ignore
+expect.extend(matchers);
+
+// Mock window.matchMedia
+Object.defineProperty(window, "matchMedia", {
+  writable: true,
+  value: vi.fn().mockImplementation((query) => ({
+    matches: false,
+    media: query,
+    onchange: null,
+    addListener: vi.fn(), // Deprecated
+    removeListener: vi.fn(), // Deprecated
+    addEventListener: vi.fn(),
+    removeEventListener: vi.fn(),
+    dispatchEvent: vi.fn(),
+  })),
+});
+
+// Mock window.location.hash
+Object.defineProperty(window, "location", {
+  writable: true,
+  value: { hash: "" },
+});
+
+afterEach(() => {
+  cleanup();
+  vi.clearAllMocks();
+  window.location.hash = "";
+});

client/src/components/RootsTab.tsx

@@ -54,6 +54,7 @@ const RootsTab = ({
             variant="destructive"
             size="sm"
             onClick={() => removeRoot(index)}
+            aria-label="Remove root"
           >
             <Minus className="h-4 w-4" />
           </Button>

client/src/components/Sidebar.tsx

@@ -1,5 +1,12 @@
 import { useState } from "react";
-import { Play, ChevronDown, ChevronRight, CircleHelp, Bug, Github } from "lucide-react";
+import {
+  Play,
+  ChevronDown,
+  ChevronRight,
+  CircleHelp,
+  Bug,
+  Github,
+} from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import {
@@ -243,18 +250,33 @@ const Sidebar = ({
           </Select>
 
           <div className="flex items-center space-x-2">
-            <a href="https://modelcontextprotocol.io/docs/tools/inspector" target="_blank" rel="noopener noreferrer">
+            <a
+              href="https://modelcontextprotocol.io/docs/tools/inspector"
+              target="_blank"
+              rel="noopener noreferrer"
+            >
               <Button variant="ghost" title="Inspector Documentation">
                 <CircleHelp className="w-4 h-4 text-gray-800" />
               </Button>
             </a>
-            <a href="https://modelcontextprotocol.io/docs/tools/debugging" target="_blank" rel="noopener noreferrer">
+            <a
+              href="https://modelcontextprotocol.io/docs/tools/debugging"
+              target="_blank"
+              rel="noopener noreferrer"
+            >
               <Button variant="ghost" title="Debugging Guide">
                 <Bug className="w-4 h-4 text-gray-800" />
               </Button>
             </a>
-            <a href="https://github.com/modelcontextprotocol/inspector" target="_blank" rel="noopener noreferrer">
-              <Button variant="ghost" title="Report bugs or contribute on GitHub">
+            <a
+              href="https://github.com/modelcontextprotocol/inspector"
+              target="_blank"
+              rel="noopener noreferrer"
+            >
+              <Button
+                variant="ghost"
+                title="Report bugs or contribute on GitHub"
+              >
                 <Github className="w-4 h-4 text-gray-800" />
               </Button>
             </a>

client/src/components/ToolsTab.tsx

@@ -174,8 +174,7 @@ const ToolsTab = ({
                           }
                           className="mt-1"
                         />
-                      ) :
-                      /* @ts-expect-error value type is currently unknown */
+                      ) : /* @ts-expect-error value type is currently unknown */
                       value.type === "object" ? (
                         <Textarea
                           id={key}

client/src/lib/hooks/useConnection.ts

@@ -44,10 +44,15 @@ export function useConnection({
   onPendingRequest,
   getRoots,
 }: UseConnectionOptions) {
-  const [connectionStatus, setConnectionStatus] = useState<"disconnected" | "connected" | "error">("disconnected");
-  const [serverCapabilities, setServerCapabilities] = useState<ServerCapabilities | null>(null);
+  const [connectionStatus, setConnectionStatus] = useState<
+    "disconnected" | "connected" | "error"
+  >("disconnected");
+  const [serverCapabilities, setServerCapabilities] =
+    useState<ServerCapabilities | null>(null);
   const [mcpClient, setMcpClient] = useState<Client | null>(null);
-  const [requestHistory, setRequestHistory] = useState<{ request: string; response?: string }[]>([]);
+  const [requestHistory, setRequestHistory] = useState<
+    { request: string; response?: string }[]
+  >([]);
 
   const pushHistory = (request: object, response?: object) => {
     setRequestHistory((prev) => [
@@ -61,7 +66,7 @@ export function useConnection({
 
   const makeRequest = async <T extends z.ZodType>(
     request: ClientRequest,
-    schema: T
+    schema: T,
   ) => {
     if (!mcpClient) {
       throw new Error("MCP client not connected");
@@ -80,14 +85,14 @@ export function useConnection({
         });
         pushHistory(request, response);
       } catch (error) {
-        const errorMessage = error instanceof Error ? error.message : String(error);
+        const errorMessage =
+          error instanceof Error ? error.message : String(error);
         pushHistory(request, { error: errorMessage });
         throw error;
       } finally {
         clearTimeout(timeoutId);
       }
 
-
       return response;
     } catch (e: unknown) {
       const errorString = (e as Error).message ?? String(e);
@@ -142,11 +147,17 @@ export function useConnection({
       const clientTransport = new SSEClientTransport(backendUrl);
 
       if (onNotification) {
-        client.setNotificationHandler(ProgressNotificationSchema, onNotification);
+        client.setNotificationHandler(
+          ProgressNotificationSchema,
+          onNotification,
+        );
       }
 
       if (onStdErrNotification) {
-        client.setNotificationHandler(StdErrNotificationSchema, onStdErrNotification);
+        client.setNotificationHandler(
+          StdErrNotificationSchema,
+          onStdErrNotification,
+        );
       }
 
       await client.connect(clientTransport);
@@ -183,6 +194,6 @@ export function useConnection({
     requestHistory,
     makeRequest,
     sendNotification,
-    connect
+    connect,
   };
 }

client/src/lib/hooks/useDraggablePane.ts

@@ -6,19 +6,28 @@ export function useDraggablePane(initialHeight: number) {
   const dragStartY = useRef<number>(0);
   const dragStartHeight = useRef<number>(0);
 
-  const handleDragStart = useCallback((e: React.MouseEvent) => {
-    setIsDragging(true);
-    dragStartY.current = e.clientY;
-    dragStartHeight.current = height;
-    document.body.style.userSelect = "none";
-  }, [height]);
+  const handleDragStart = useCallback(
+    (e: React.MouseEvent) => {
+      setIsDragging(true);
+      dragStartY.current = e.clientY;
+      dragStartHeight.current = height;
+      document.body.style.userSelect = "none";
+    },
+    [height],
+  );
 
-  const handleDragMove = useCallback((e: MouseEvent) => {
-    if (!isDragging) return;
-    const deltaY = dragStartY.current - e.clientY;
-    const newHeight = Math.max(100, Math.min(800, dragStartHeight.current + deltaY));
-    setHeight(newHeight);
-  }, [isDragging]);
+  const handleDragMove = useCallback(
+    (e: MouseEvent) => {
+      if (!isDragging) return;
+      const deltaY = dragStartY.current - e.clientY;
+      const newHeight = Math.max(
+        100,
+        Math.min(800, dragStartHeight.current + deltaY),
+      );
+      setHeight(newHeight);
+    },
+    [isDragging],
+  );
 
   const handleDragEnd = useCallback(() => {
     setIsDragging(false);
@@ -39,6 +48,6 @@ export function useDraggablePane(initialHeight: number) {
   return {
     height,
     isDragging,
-    handleDragStart
+    handleDragStart,
   };
 }

client/src/main.tsx

@@ -1,7 +1,7 @@
 import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";
-import { ToastContainer } from 'react-toastify';
-import 'react-toastify/dist/ReactToastify.css';
+import { ToastContainer } from "react-toastify";
+import "react-toastify/dist/ReactToastify.css";
 import App from "./App.tsx";
 import "./index.css";
 

client/vitest.config.ts

@@ -0,0 +1,19 @@
+/// <reference types="vitest" />
+import { defineConfig } from 'vite'
+import react from '@vitejs/plugin-react'
+import path from 'path'
+
+export default defineConfig({
+  plugins: [react()],
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, './src'),
+    },
+  },
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    setupFiles: ['./src/__tests__/setup/setup.ts'],
+    include: ['src/__tests__/**/*.{test,spec}.{js,mjs,cjs,ts,mts,cts,jsx,tsx}'],
+  },
+})