add test for #891

Author: Rich-Harris

test/runtime/samples/set-mutated-data/_config.js

@@ -0,0 +1,14 @@
+const data = { foo: 0 };
+
+export default {
+	data,
+
+	html: '0',
+
+	test(assert, component, target) {
+		data.foo = 42;
+		component.set(data);
+
+		assert.htmlEqual(target.innerHTML, '42');
+	}
+};

test/runtime/samples/set-mutated-data/main.html

@@ -0,0 +1 @@
+{{foo}}