test: add test cases

Author: ota-meshi

Diff for: tests/fixtures/parser/ast/svelte5/svelte-ts-$derived01-input.svelte.ts

@@ -0,0 +1,15 @@
+export function createCounterDouble() {
+  let count = $state(0);
+  const doubled = $derived(count * 2);
+
+	function increment() {
+		count += 1;
+	}
+
+	return {
+		get doubled() {
+			return doubled;
+		},
+		increment
+	};
+}