test: 添加完整测试套件（52 个文件，326 个用例）

基于 Vitest 搭建测试基础设施，覆盖后端纯函数、API 路由、
前端 hooks、UI 组件和页面级集成测试。

src/hooks/useRoomPolling.test.ts

@@ -0,0 +1,91 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { renderHook, waitFor, act } from "@testing-library/react";
+
+let esInstances: { onmessage?: (e: MessageEvent) => void; onerror?: () => void; onopen?: () => void; close: ReturnType<typeof vi.fn> }[] = [];
+
+class MockEventSource {
+  onmessage: ((e: MessageEvent) => void) | null = null;
+  onerror: (() => void) | null = null;
+  onopen: (() => void) | null = null;
+  close = vi.fn();
+
+  constructor(_url: string) {
+    esInstances.push(this);
+  }
+}
+
+vi.stubGlobal("EventSource", MockEventSource);
+
+vi.mock("swr", () => ({
+  default: vi.fn().mockReturnValue({
+    data: {
+      roomId: "ROOM01",
+      userCount: 2,
+      match: null,
+      matchType: null,
+      matchLikes: 0,
+      runnerUps: [],
+      likeCounts: {},
+      swipeCounts: {},
+      restaurants: [],
+      creatorId: "user-1",
+      locked: false,
+      users: ["user-1", "user-2"],
+      userProfiles: {},
+      scene: "eat",
+    },
+    error: null,
+    isLoading: false,
+    mutate: vi.fn(),
+  }),
+}));
+
+import { useRoomPolling } from "./useRoomPolling";
+
+beforeEach(() => {
+  esInstances = [];
+});
+
+afterEach(() => {
+  vi.clearAllMocks();
+});
+
+describe("useRoomPolling", () => {
+  it("returns room data from SWR", () => {
+    const { result } = renderHook(() => useRoomPolling("ROOM01"));
+
+    expect(result.current.userCount).toBe(2);
+    expect(result.current.users).toEqual(["user-1", "user-2"]);
+    expect(result.current.scene).toBe("eat");
+  });
+
+  it("creates EventSource connection", () => {
+    renderHook(() => useRoomPolling("ROOM01"));
+    expect(esInstances.length).toBeGreaterThan(0);
+  });
+
+  it("returns defaults when no roomId", () => {
+    const { result } = renderHook(() => useRoomPolling(undefined));
+    expect(result.current.userCount).toBe(2);
+  });
+
+  it("returns notFound from error state", async () => {
+    const useSWR = vi.mocked((await import("swr")).default);
+    useSWR.mockReturnValue({
+      data: undefined,
+      error: new Error("NOT_FOUND"),
+      isLoading: false,
+      mutate: vi.fn(),
+    } as never);
+
+    const { result } = renderHook(() => useRoomPolling("ROOM01"));
+    expect(result.current.notFound).toBe(true);
+  });
+
+  it("cleans up EventSource on unmount", () => {
+    const { unmount } = renderHook(() => useRoomPolling("ROOM01"));
+    const es = esInstances[esInstances.length - 1];
+    unmount();
+    expect(es.close).toHaveBeenCalled();
+  });
+});