add test

packages/svelte/tests/runtime-runes/samples/async-effect-after-boundary/Child.svelte

@@ -0,0 +1,5 @@
+<script>
+	$effect(() => {
+		console.log('in effect')
+	});
+</script>

packages/svelte/tests/runtime-runes/samples/async-effect-after-boundary/_config.js

@@ -0,0 +1,16 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target, logs }) {
+		const [shift] = target.querySelectorAll('button');
+
+		await tick();
+		assert.deepEqual(logs, []);
+
+		shift.click();
+		await tick();
+
+		assert.deepEqual(logs, ['in effect']);
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-effect-after-boundary/main.svelte

@@ -0,0 +1,22 @@
+<script>
+	import Child from './Child.svelte';
+
+	let resolvers = [];
+
+	function push(value) {
+		const { promise, resolve } = Promise.withResolvers();
+		resolvers.push(() => resolve(value));
+		return promise;
+	}
+</script>
+
+<button onclick={() => resolvers.shift()?.()}>shift</button>
+
+<svelte:boundary>
+	<p>{await push('hello')}</p>
+	<Child />
+
+	{#snippet pending()}
+		<p>loading...</p>
+	{/snippet}
+</svelte:boundary>