tests/basics: Improve runtime.c test coverage.

tests/basics/fun_calldblstar3.py

@@ -5,7 +5,8 @@ def foo(**kw):
 
 class Mapping:
     def keys(self):
-        return ['a', 'b', 'c']
+        # the long string checks the case of string interning
+        return ['a', 'b', 'c', 'abcdefghijklmnopqrst']
 
     def __getitem__(self, key):
         if key == 'a':

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:

tests/basics/iter0.py

@@ -4,3 +4,6 @@ try:
         pass
 except TypeError:
     print('TypeError')
+
+# builtin type that is iterable, calling __next__ explicitly
+print(iter(range(4)).__next__())