enhance test

packages/svelte/tests/runtime-runes/samples/async-attachment/_config.js

@@ -4,6 +4,15 @@ import { test } from '../../test';
 export default test({
 	async test({ assert, target }) {
 		await tick();
-		assert.htmlEqual(target.innerHTML, '<p>foo</p><div>foo</div>');
+		assert.htmlEqual(target.innerHTML, '<button>toggle</button> <p>foo</p><div>foo</div>');
+
+		const [toggle] = target.querySelectorAll('button');
+		toggle.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<button>toggle</button>');
+
+		toggle.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<button>toggle</button> <p>foo</p><div>foo</div>');
 	}
 });

packages/svelte/tests/runtime-runes/samples/async-attachment/main.svelte

@@ -1,9 +1,14 @@
 <script>
 	import Inner from './Inner.svelte';
+
+	let show = $state(true);
 </script>
 
 <svelte:boundary>
+	<button onclick={() => show = !show}>toggle</button>
+	{#if show}
 		<Inner />
+	{/if}
 
 	{#snippet pending()}
 		<p>pending</p>