extended docstring test

tests/run/r_docstrings.pyx

 __doc__ = """
     >>> print f.__doc__
     This is a function docstring.
+
     >>> print C.__doc__
     This is a class docstring.
+    >>> print CS.__doc__
+    This is a subclass docstring.
+    >>> print CSS.__doc__
+    None
+
     >>> print T.__doc__
     This is an extension type docstring.
+    >>> print TS.__doc__
+    This is an extension subtype docstring.
+    >>> print TSS.__doc__
+    None
+
+Compare with standard Python:
+
+    >>> def f():
+    ...     "This is a function docstring."
+    >>> print f.__doc__
+    This is a function docstring.
+
+    >>> class C:
+    ...     "This is a class docstring."
+    >>> class CS(C):
+    ...     "This is a subclass docstring."
+    >>> class CSS(CS):
+    ...     pass
+
+    >>> print C.__doc__
+    This is a class docstring.
+    >>> print CS.__doc__
+    This is a subclass docstring.
+    >>> print CSS.__doc__
+    None
 """
 
 def f():
@@ -13,6 +44,17 @@ def f():
 class C:
     "This is a class docstring."
 
+class CS(C):
+    "This is a subclass docstring."
+
+class CSS(CS):
+    pass
+
 cdef class T:
     "This is an extension type docstring."
 
+cdef class TS(T):
+    "This is an extension subtype docstring."
+
+cdef class TSS(TS):
+    pass