improved component composition and added tests.

vite.config.ts

@@ -1,21 +1,27 @@
-import { defineConfig } from 'vite'
+import { defineConfig } from 'vitest/config'
 import { svelte } from '@sveltejs/vite-plugin-svelte'
+import { svelteTesting } from '@testing-library/svelte/vite'
 import { fileURLToPath, URL } from 'node:url'
 
 // Fully static output: the app talks to a Mastodon/Pleroma server directly from
 // the browser, so `dist/` can be dropped on any static host (or file://-ish CDN).
 export default defineConfig({
   base: './',
-  plugins: [svelte()],
+  plugins: [svelte(), svelteTesting()],
   resolve: {
     alias: {
       $lib: fileURLToPath(new URL('./src/lib', import.meta.url)),
       $components: fileURLToPath(new URL('./src/components', import.meta.url)),
       $routes: fileURLToPath(new URL('./src/routes', import.meta.url)),
+      $test: fileURLToPath(new URL('./src/test', import.meta.url)),
     },
   },
   build: {
     target: 'es2022',
     cssCodeSplit: false,
   },
+  test: {
+    environment: 'jsdom',
+    setupFiles: ['./src/test/setup.ts'],
+  },
 })