tests/basics: Improve runtime.c test coverage.

tests/basics/fun_callstar.py

@@ -17,6 +17,11 @@ foo(*range(3))
 # pos then iterator
 foo(1, *range(2, 4))
 
+# an iterator with many elements
+def foo(*rest):
+    print(rest)
+foo(*range(10))
+
 # method calls with *pos
 
 class A: