test: add unit test for ChatMessageDisplay

client/vite.config.ts

@@ -1,3 +1,4 @@
+/// <reference types="vitest/config" />
 import { defineConfig } from "vite";
 import react from "@vitejs/plugin-react";
 import tailwindcss from "@tailwindcss/vite";
@@ -5,6 +6,10 @@ import tailwindcss from "@tailwindcss/vite";
 // https://vite.dev/config/
 export default defineConfig({
   plugins: [react(), tailwindcss()],
+  test: {
+    globals: true,
+    environment: "jsdom",
+  },
   server: {
     proxy: {
       "/ws": {