added test

packages/svelte/tests/hydration/samples/removes-undefined-attributes/_config.js

@@ -0,0 +1,11 @@
+import { test } from '../../test';
+
+export default test({
+	server_props: {
+		browser: false
+	},
+
+	props: {
+		browser: true
+	}
+});

packages/svelte/tests/hydration/samples/removes-undefined-attributes/_expected.html

@@ -0,0 +1 @@
+<!--[--><div></div><!--]-->

packages/svelte/tests/hydration/samples/removes-undefined-attributes/main.svelte

@@ -0,0 +1,9 @@
+<script>
+	const { browser } = $props();
+
+	const attributes = {
+		"data-test": browser ? undefined : ""
+	};
+</script>
+
+<div {...attributes}></div>