chore: better test case

closes #10129

packages/svelte/tests/runtime-legacy/samples/reactive-value-assign-properties/_config.js

@@ -1,5 +1,37 @@
+import { flushSync } from 'svelte';
 import { test } from '../../test';
 
 export default test({
-	html: `1 1`
+	html: `<button>false</button><button>false</button><button>false</button><button>false</button>`,
+	test({ assert, target }) {
+		const [button1, button2, button3, button4] = target.querySelectorAll('button');
+
+		button1.click();
+		flushSync();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>true</button><button>false</button><button>false</button><button>false</button>`
+		);
+
+		button2.click();
+		flushSync();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>true</button><button>true</button><button>false</button><button>false</button>`
+		);
+
+		button3.click();
+		flushSync();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>true</button><button>true</button><button>true</button><button>false</button>`
+		);
+
+		button4.click();
+		flushSync();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>true</button><button>true</button><button>true</button><button>true</button>`
+		);
+	}
 });

packages/svelte/tests/runtime-legacy/samples/reactive-value-assign-properties/main.svelte

@@ -1,12 +1,15 @@
 <script>
-	let button = { title: '', label: '' };
-	let title = '';
-	let label = '';
-
-	title = label = '1'; // to add dependencies/generate update block
-
-	$: button.title = title;
-	$: button.label = label;
+	let array;
+	$: {
+		// test that this doesn't rerun on array change
+		array = []
+		array[0] = [false, false];
+		array[1] = [false, false];
+	}
 </script>
 
-{button.title} {button.label}
+{#each array as row, i}
+	{#each row as item, j}
+		<button on:click={() => array[i][j] = !array[i][j]}>{item}</button>
+	{/each}
+{/each}