Add a test..

test/js/samples/css-custom-element-no-shadow-dom/_config.js

@@ -0,0 +1,6 @@
+export default {
+	options: {
+		customElement: true,
+		shadowDom: false
+	}
+};

test/js/samples/css-custom-element-no-shadow-dom/expected.js

@@ -0,0 +1,54 @@
+/* generated by Svelte vX.Y.Z */
+import {
+	SvelteElement,
+	detach,
+	element,
+	init,
+	insert,
+	noop,
+	safe_not_equal
+} from "svelte/internal";
+
+function create_fragment(ctx) {
+	var h1;
+
+	return {
+		c() {
+			h1 = element("h1");
+			h1.textContent = "Hello world";
+			this.c = noop;
+		},
+
+		m(target, anchor) {
+			insert(target, h1, anchor);
+		},
+
+		p: noop,
+		i: noop,
+		o: noop,
+
+		d(detaching) {
+			if (detaching) {
+				detach(h1);
+			}
+		}
+	};
+}
+
+class Component extends SvelteElement {
+	constructor(options) {
+		super({ use_shadow_dom: true });
+
+		init(this, { target: this }, null, create_fragment, safe_not_equal, []);
+
+		if (options) {
+			if (options.target) {
+				insert(options.target, this, options.anchor);
+			}
+		}
+	}
+}
+
+customElements.define("custom-element", Component);
+
+export default Component;

test/js/samples/css-custom-element-no-shadow-dom/input.svelte

@@ -0,0 +1,9 @@
+<svelte:options tag="custom-element"/>
+
+<h1>Hello world</h1>
+
+<style>
+h1 { 
+  color: blue;
+}
+</style>