Improve pass-by-reference test

able-script-test/pass-by-reference.able

@@ -12,6 +12,14 @@ var bar = "world";
 
 swap(foo, bar);
 
-owo Should print "hello", then "world"
-bar print;
+if (foo != "world") {
+    "FAILED" print;
+    "foo should be 'world', is actually:" print;
     foo print;
+}
+
+owo AbleScript doesn't have an `else` statement (yet), so we get to
+owo check the reverse condition.
+if (foo == "world") {
+    "OK" print;
+}