tests/render-in-iframe: added failing test for rendering in another document

test/generator/render-in-iframe/_config.js

@@ -0,0 +1,21 @@
+export default {
+	test ( assert, component, target, window ) {
+		const iframe = window.document.createElement('iframe');
+		window.document.body.appendChild(iframe);
+
+		const otherTarget = iframe.contentWindow.document.body;
+
+		new component.constructor({
+			target: otherTarget
+		});
+
+		assert.equal(
+			window.getComputedStyle(target.querySelector('h1')).color,
+			'rgb(255, 0, 0)'
+		);
+		assert.equal(
+			window.getComputedStyle(otherTarget.querySelector('h1')).color,
+			'rgb(255, 0, 0)'
+		);
+	}
+};

test/generator/render-in-iframe/main.html

@@ -0,0 +1,6 @@
+<h1>Just some static HTML</h1>
+<style>
+h1 {
+	color: rgb(255, 0, 0);
+}
+</style>