test: Add hidden attribute test

test/runtime/samples/attribute-boolean-hidden/_config.js

@@ -0,0 +1,10 @@
+export default {
+	props: {
+		hidden: true
+	},
+	html: '<div hidden />',
+	test({ assert, component, target }) {
+		component.hidden = false;
+		assert.htmlEqual(target.innerHTML, '<div />');
+	}
+};

test/runtime/samples/attribute-boolean-hidden/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let hidden = false;
+</script>
+
+<div {hidden} />