failing test for linear order

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

@@ -0,0 +1,42 @@
+import { flushSync, tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [a, b, reset1, reset2, resolve1, resolve2] = target.querySelectorAll('button');
+
+		flushSync(() => resolve1.click());
+		await Promise.resolve();
+		await Promise.resolve();
+		await Promise.resolve();
+		await tick();
+		flushSync();
+
+		const p = /** @type {HTMLElement} */ (target.querySelector('#test'));
+
+		assert.htmlEqual(p.innerHTML, '1 + 2 = 3');
+
+		flushSync(() => reset1.click());
+		flushSync(() => a.click());
+		flushSync(() => reset2.click());
+		flushSync(() => b.click());
+
+		flushSync(() => resolve2.click());
+		await Promise.resolve();
+		await Promise.resolve();
+		await Promise.resolve();
+		await tick();
+		flushSync();
+
+		assert.htmlEqual(p.innerHTML, '1 + 2 = 3');
+
+		flushSync(() => resolve1.click());
+		await Promise.resolve();
+		await Promise.resolve();
+		await Promise.resolve();
+		await tick();
+		flushSync();
+
+		assert.htmlEqual(p.innerHTML, '2 + 3 = 5');
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-linear-order/main.svelte

@@ -0,0 +1,31 @@
+<script>
+	let delay = 1000;
+	let a = $state(1);
+	let b = $state(2);
+
+	let d1 = Promise.withResolvers();
+	let d2 = Promise.withResolvers();
+	let deferred = d1;
+
+	async function add(a, b) {
+		await deferred.promise;
+		return a + b;
+	}
+</script>
+
+<button onclick={() => a++}>a++</button>
+<button onclick={() => b++}>b++</button>
+
+<button onclick={() => deferred = d1 = Promise.withResolvers()}>reset 1</button>
+<button onclick={() => deferred = d2 = Promise.withResolvers()}>reset 2</button>
+
+<button onclick={() => d1.resolve()}>resolve 1</button>
+<button onclick={() => d2.resolve()}>resolve 2</button>
+
+<svelte:boundary>
+	<p id="test">{a} + {b} = {await add(a, b)}</p>
+
+	{#snippet pending()}
+		<p>loading...</p>
+	{/snippet}
+</svelte:boundary>