From 42268ee5bd945f5df4c9b2e459dec46f4b1b2435 Mon Sep 17 00:00:00 2001
From: Simon Holthausen <simon.holthausen@vercel.com>
Date: Fri, 10 Jul 2026 16:46:43 +0200
Subject: [PATCH] chore: add some failing tests

During my explorations I collected these new tests which are currently failing. Two of them work on the incremental-batches branch, all of them (adjusted for new behavior) pass on my uncommitted entangle batches branch, and all of them also pass on another uncommitted experimental branch of overlaying deriveds which will likely not land.
---
 .../_config.js                                | 42 +++++++++++++++++++
 .../main.svelte                               | 23 ++++++++++
 .../async-derived-not-overfiring/_config.js   | 35 ++++++++++++++++
 .../async-derived-not-overfiring/main.svelte  | 29 +++++++++++++
 .../async-derived-not-underfiring/_config.js  | 28 +++++++++++++
 .../async-derived-not-underfiring/main.svelte | 22 ++++++++++
 6 files changed, 179 insertions(+)
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-derived-log-outside-reactivity/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-derived-log-outside-reactivity/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-derived-not-underfiring/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-derived-not-underfiring/main.svelte

diff --git a/packages/svelte/tests/runtime-runes/samples/async-derived-log-outside-reactivity/_config.js b/packages/svelte/tests/runtime-runes/samples/async-derived-log-outside-reactivity/_config.js
new file mode 100644
index 0000000000..1a7ed0eb92
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-derived-log-outside-reactivity/_config.js
@@ -0,0 +1,42 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	skip: true, // TODO fix
+	async test({ assert, target, logs }) {
+		await tick();
+
+		const [a, b, log, resolve] = target.querySelectorAll('button');
+		const [p] = target.querySelectorAll('p');
+
+		a.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, '0 0 0');
+
+		b.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, '0 0 0');
+
+		log.click();
+		await tick();
+		assert.deepEqual(logs, [0, 2]);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, '1 0 1');
+		assert.deepEqual(logs, [0, 2, 1]);
+
+		log.click();
+		await tick();
+		assert.deepEqual(logs, [0, 2, 1, 2]);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, '1 1 2');
+		assert.deepEqual(logs, [0, 2, 1, 2, 2]);
+
+		log.click();
+		await tick();
+		assert.deepEqual(logs, [0, 2, 1, 2, 2, 2]);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-derived-log-outside-reactivity/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-derived-log-outside-reactivity/main.svelte
new file mode 100644
index 0000000000..bf543ba595
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-derived-log-outside-reactivity/main.svelte
@@ -0,0 +1,23 @@
+<script>
+	let a = $state(0);
+	let b = $state(0);
+
+	let d = $derived(a + b);
+
+	let queued = [];
+	function push(v) {
+		if (!v) return v;
+		return new Promise((resolve) => {
+			queued.push(() => resolve(v));
+		});
+	}
+
+	$effect(() => console.log(d));
+</script>
+
+<button onclick={() => a++}>a++</button>
+<button onclick={() => b++}>b++</button>
+<button onclick={() => console.log(d)}>log d</button>
+<button onclick={() => queued.shift()?.()}>resolve</button>
+
+<p>{await push(a)} {await push(b)} {d}</p>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring/_config.js b/packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring/_config.js
new file mode 100644
index 0000000000..b959ba5407
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring/_config.js
@@ -0,0 +1,35 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	skip: true, // TODO fix
+	async test({ assert, target, logs }) {
+		await tick();
+
+		const [a, b, log, resolve] = target.querySelectorAll('button');
+		const [div] = target.querySelectorAll('div');
+
+		assert.deepEqual(logs, ['e1 0', 'e2 0']);
+		logs.length = 0;
+
+		a.click();
+		await tick();
+		assert.htmlEqual(div.innerHTML, '<p>0</p> <p>0</p> <p>0</p>');
+
+		b.click();
+		await tick();
+		assert.htmlEqual(div.innerHTML, '<p>0</p> <p>1</p> <p>1</p>');
+
+		log.click();
+		await tick();
+		assert.deepEqual(logs, ['e1 1', 'e2 1', 'runs 2']); // ideally it's only 2 runs, one or two more would also be acceptable but not the 8 that it's today
+		logs.length = 0;
+
+		resolve.click();
+		await tick();
+		log.click();
+		await tick();
+		assert.htmlEqual(div.innerHTML, '<p>1</p> <p>2</p> <p>2</p>');
+		assert.deepEqual(logs, ['e1 2', 'e2 2', 'runs 3']);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring/main.svelte
new file mode 100644
index 0000000000..784932ab5d
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring/main.svelte
@@ -0,0 +1,29 @@
+<script>
+	let a = $state(0);
+	let b = $state(0);
+	let runs = 0;
+
+	let d = $derived((runs++, a + b));
+
+	const queued = [];
+	function push(v) {
+		if (!v) return v;
+		return new Promise((resolve) => {
+			queued.push(() => resolve(v));
+		});
+	}
+
+	$effect(() => console.log('e1 ' + d));
+	$effect(() => console.log('e2 ' + d));
+</script>
+
+<button onclick={() => a++}>a++</button>
+<button onclick={() => b++}>b++</button>
+<button onclick={() => console.log('runs ' + runs)}>log runs</button>
+<button onclick={() => queued.shift()?.()}>resolve</button>
+
+<div>
+	<p>{await push(a)}</p>
+	<p>{d}</p>
+	<p>{d}</p>
+</div>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-derived-not-underfiring/_config.js b/packages/svelte/tests/runtime-runes/samples/async-derived-not-underfiring/_config.js
new file mode 100644
index 0000000000..7d31d30b46
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-derived-not-underfiring/_config.js
@@ -0,0 +1,28 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	skip: true, // TODO fix
+	async test({ assert, target, logs }) {
+		await tick();
+
+		const [a, b, resolve] = target.querySelectorAll('button');
+		const [p] = target.querySelectorAll('p');
+
+		assert.deepEqual(logs, ['b: 0, d: 0']);
+		logs.length = 0;
+
+		a.click();
+		await tick();
+		b.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, '0 1');
+		assert.deepEqual(logs, ['b: 1, d: 0']);
+		logs.length = 0;
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, '2 1');
+		assert.deepEqual(logs, ['b: 1, d: 2']);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-derived-not-underfiring/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-derived-not-underfiring/main.svelte
new file mode 100644
index 0000000000..97d91ae994
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-derived-not-underfiring/main.svelte
@@ -0,0 +1,22 @@
+<script>
+	let a = $state(0);
+	let b = $state(0);
+
+	let d = $derived(a * 2);
+
+	const queued = [];
+	function push(v) {
+		if (!v) return v;
+		return new Promise((resolve) => {
+			queued.push(() => resolve(v));
+		});
+	}
+
+	$effect(() => console.log(`b: ${b}, d: ${d}`));
+</script>
+
+<button onclick={() => a++}>a++</button>
+<button onclick={() => b++}>b++</button>
+<button onclick={() => queued.shift()?.()}>resolve</button>
+
+<p>{await push(d)} {b}</p>