diff --git a/scripts/fib.toy b/scripts/fib.toy
index ef59c88..d2c85fe 100644
--- a/scripts/fib.toy
+++ b/scripts/fib.toy
@@ -1,3 +1,4 @@
+//WARNING: please think twice before using this in a test
 fn fib(n : int) {
 	if (n < 2) return n;
 	return fib(n-1) + fib(n-2);
diff --git a/test/scripts/runner_sample_code.toy b/test/scripts/runner_sample_code.toy
index 0c3e342..b41a5ae 100644
--- a/test/scripts/runner_sample_code.toy
+++ b/test/scripts/runner_sample_code.toy
@@ -1,12 +1,21 @@
-fn fib(n : int) {
-    if (n < 2) {
-        return n;
-    }
+//memoize the fib function
+var memo: [int : int] = [:];
 
-    return fib(n-1) + fib(n-2);
+fn fib(n : int) {
+	if (n < 2) {
+		return n;
+	}
+
+	var result = memo[n];
+	if (result == null) {
+		result = fib(n-1) + fib(n-2);
+		memo[n] = result;
+	}
+
+	return result;
 }
 
-for (var i = 0; i < 20; i++) {
+for (var i = 0; i < 40; i++) {
 	var res = fib(i);
 	print string i + ": " + string res;
 }
\ No newline at end of file