add test

test/runtime/samples/store-auto-subscribe-nullish/_config.js

@@ -0,0 +1,13 @@
+import { writable } from '../../../../store';
+
+export default {
+	html: `
+		<p>undefined</p>
+	`,
+	async test({ assert, component, target }) {
+		component.store = writable('foo');
+		assert.htmlEqual(target.innerHTML, `
+			<p>foo</p>
+		`);
+	}
+};

test/runtime/samples/store-auto-subscribe-nullish/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let store;
+</script>
+
+<p>{$store}</p>