add test

test/runtime/samples/spread-element-class/_config.js

@@ -0,0 +1,7 @@
+export default {
+	html: `<div class='foo bar'>hello</div>`,
+	test({ assert, component, target }) {
+		component.blah = 'goodbye';
+		assert.htmlEqual(target.innerHTML, `<div class='foo bar'>goodbye</div>`);
+	}
+};

test/runtime/samples/spread-element-class/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let blah = 'hello';
+</script>
+
+<div class='foo' class:bar={true} {...{}}>{blah}</div>