test that private state doesnt leak into parent

test/runtime/samples/component-binding-private-state/Bar.html

@@ -0,0 +1,5 @@
+<script>
+	let x = 'no';
+</script>
+
+<p>Bar: {x}</p>

test/runtime/samples/component-binding-private-state/Foo.html

@@ -0,0 +1,5 @@
+<script>
+	let x = 'yes';
+</script>
+
+<p>Foo: {x}</p>

test/runtime/samples/component-binding-private-state/_config.js

@@ -0,0 +1,31 @@
+export default {
+	html: `
+		<p>Foo: yes</p>
+		<p>x in parent: undefined</p>
+	`,
+
+	async test({ assert, component, target, window }) {
+		component.a = false;
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>Bar: no</p>
+			<p>x in parent: undefined</p>
+		`);
+
+		component.a = true;
+		assert.equal(component.x, undefined);
+		component.x = 'maybe';
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>Foo: yes</p>
+			<p>x in parent: maybe</p>
+		`);
+
+		component.a = false;
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>Bar: no</p>
+			<p>x in parent: maybe</p>
+		`);
+	}
+};

test/runtime/samples/component-binding-private-state/main.html

@@ -0,0 +1,11 @@
+<script>
+	import Foo from './Foo.html';
+	import Bar from './Bar.html';
+
+	export let a = true;
+	export let x;
+</script>
+
+<svelte:component this="{a ? Foo : Bar}" bind:x/>
+
+<p>x in parent: {x}</p>