Make all tests not output anything

tests/advanced6.rs

@@ -4,8 +4,9 @@ use std::sync::{Arc, Mutex};
 use std::io::{Cursor, Seek, SeekFrom, Read};
 
 fn run_calc(input: &'static str, expected: &str) {
-    let rc = Arc::new(Mutex::new(Cursor::new(Vec::new())));
+    let rc = rustijvm::stubs::output_stub();
     let mut machine = rustijvm::Machine::new_from_file("files/advanced/SimpleCalc.ijvm").unwrap();
+
     machine.set_input(Box::new(input.as_bytes()));
     machine.set_output(rc.clone());
     machine.run().unwrap();
@@ -33,3 +34,8 @@ fn advanced6_recurse2() {
 fn advanced6_recurse3() {
     run_calc("8!?.", "40320\n");
 }
+
+#[test]
+fn advanced6_recurse4() {
+    run_calc("5!5+?.", "125\n");
+}