add test

Author: Rich-Harris

packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/_config.js

@@ -0,0 +1,20 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	test({ assert, target, logs }) {
+		const button = target.querySelector('button');
+
+		flushSync(() => button?.click());
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>increment</button>
+				<p>1/2</p
+			`
+		);
+
+		assert.deepEqual(logs, [0, 0]);
+	}
+});

packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/main.svelte

@@ -0,0 +1,26 @@
+<script>
+	class Foo {
+		value = $state(0);
+		double = $derived(this.value * 2);
+
+		constructor() {
+			console.log(this.value, this.double);
+		}
+
+		increment() {
+			this.value++;
+		}
+	}
+
+	let foo = $state();
+
+	$effect(() => {
+		foo = new Foo();
+	});
+</script>
+
+<button onclick={() => foo.increment()}>increment</button>
+
+{#if foo}
+	<p>{foo.value}/{foo.double}</p>
+{/if}