add test that fails on main

packages/svelte/tests/runtime-legacy/samples/each-blocks-update/_config.js

@@ -0,0 +1,27 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	html: `
+		<button>1</button>
+		<button>2</button>
+		<button>3</button>
+		<p>1, 2, 3</p>
+	`,
+
+	test({ assert, target }) {
+		let buttons = target.querySelectorAll('button');
+
+		flushSync(() => buttons[2].click());
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>1</button>
+				<button>2</button>
+				<button>4</button>
+				<p>1, 2, 4</p>
+			`
+		);
+	}
+});

packages/svelte/tests/runtime-legacy/samples/each-blocks-update/main.svelte

@@ -0,0 +1,9 @@
+<script>
+	let arr = [1, 2, 3];
+</script>
+
+{#each arr as n}
+	<button on:click={() => n++}>{n}</button>
+{/each}
+
+<p>{arr.join(', ')}</p>