Doctest now examines all docstrings by default. Previously, it would

skip over functions with private names (as indicated by the underscore
naming convention).  The old default created too much of a risk that
user tests were being skipped inadvertently.  Note, this change could
break code in the unlikely case that someone had intentionally put
failing tests in the docstrings of private functions.  The breakage
is easily fixable by specifying the old behavior when calling testmod()
or Tester().  The more likely case is that the silent failure was
unintended and that the user needed to be informed so the test could be
fixed.

Doc/lib/libdoctest.tex

@@ -190,15 +190,16 @@ attempted.
 
 See \file{docstring.py} for all the details.  They're unsurprising:  the
 module docstring, and all function, class and method docstrings are
-searched, with the exception of docstrings attached to objects with private
-names.  Objects imported into the module are not searched.
+searched.  Optionally, the tester can be directed to exclude
+docstrings attached to objects with private names.
+Objects imported into the module are not searched.
 
 In addition, if \code{M.__test__} exists and "is true", it must be a
 dict, and each entry maps a (string) name to a function object, class
 object, or string.  Function and class object docstrings found from
-\code{M.__test__} are searched even if the name is private, and
-strings are searched directly as if they were docstrings.  In output,
-a key \code{K} in \code{M.__test__} appears with name
+\code{M.__test__} are searched even if the the tester has been
+directly to skip over private names in the rest of the module.
+In output, a key \code{K} in \code{M.__test__} appears with name
 
 \begin{verbatim}
       <name of M>.__test__.K
@@ -206,7 +207,7 @@ a key \code{K} in \code{M.__test__} appears with name
 
 Any classes found are recursively searched similarly, to test docstrings in
 their contained methods and nested classes.  While private names reached
-from \module{M}'s globals are skipped, all names reached from
+from \module{M}'s globals can be optionally skipped, all names reached from
 \code{M.__test__} are searched.
 
 \subsection{What's the Execution Context?}

Lib/doctest.py

@@ -48,10 +48,10 @@ WHICH DOCSTRINGS ARE EXAMINED?
 + M.__doc__.
 
 + f.__doc__ for all functions f in M.__dict__.values(), except those
-  with private names and those defined in other modules.
+  defined in other modules.
 
-+ C.__doc__ for all classes C in M.__dict__.values(), except those with
-  private names and those defined in other modules.
++ C.__doc__ for all classes C in M.__dict__.values(), except those
+  defined in other modules.
 
 + If M.__test__ exists and "is true", it must be a dict, and
   each entry maps a (string) name to a function object, class object, or
@@ -62,13 +62,16 @@ WHICH DOCSTRINGS ARE EXAMINED?
       <name of M>.__test__.K
 
 Any classes found are recursively searched similarly, to test docstrings in
-their contained methods and nested classes.  Private names reached from M's
-globals are skipped, but all names reached from M.__test__ are searched.
+their contained methods and nested classes.  All names reached from
+M.__test__ are searched.
 
-By default, a name is considered to be private if it begins with an
-underscore (like "_my_func") but doesn't both begin and end with (at least)
-two underscores (like "__init__").  You can change the default by passing
-your own "isprivate" function to testmod.
+Optionally, functions with private names can be skipped (unless listed in
+M.__test__) by supplying a function to the "isprivate" argument that will
+identify private functions.  For convenience, one such function is
+supplied.  docttest.is_private considers a name to be private if it begins
+with an underscore (like "_my_func") but doesn't both begin and end with
+(at least) two underscores (like "__init__").  By supplying this function
+or your own "isprivate" function to testmod, the behavior can be customized.
 
 If you want to test docstrings in objects with private names too, stuff
 them into an M.__test__ dict, or see ADVANCED USAGE below (e.g., pass your
@@ -671,8 +674,10 @@ Optional keyword arg "verbose" prints lots of stuff if true, only
 failures if false; by default, it's true iff "-v" is in sys.argv.
 
 Optional keyword arg "isprivate" specifies a function used to determine
-whether a name is private.  The default function is doctest.is_private;
-see its docs for details.
+whether a name is private.  The default function is to assume that
+no functions are private.  The "isprivate" arg may be set to
+doctest.is_private in order to skip over functions marked as private
+using an underscore naming convention; see its docs for details.
 
 See doctest.testmod docs for the meaning of optionflags.
 """
@@ -691,8 +696,9 @@ See doctest.testmod docs for the meaning of optionflags.
             verbose = "-v" in sys.argv
         self.verbose = verbose
 
+        # By default, assume that nothing is private
         if isprivate is None:
-            isprivate = is_private
+            isprivate = lambda prefix, base:  0
         self.isprivate = isprivate
 
         self.optionflags = optionflags
@@ -861,26 +867,26 @@ See doctest.testmod docs for the meaning of optionflags.
 
         Tests that objects outside m1 are excluded:
 
-        >>> t = Tester(globs={}, verbose=0)
+        >>> t = Tester(globs={}, verbose=0, isprivate=is_private)
         >>> t.rundict(m1.__dict__, "rundict_test", m1)  # _f, f2 and g2 and h2 skipped
         (0, 3)
 
-        Again, but with a custom isprivate function allowing _f:
+        Again, but with the default isprivate function allowing _f:
 
-        >>> t = Tester(globs={}, verbose=0, isprivate=lambda x,y: 0)
+        >>> t = Tester(globs={}, verbose=0)
         >>> t.rundict(m1.__dict__, "rundict_test_pvt", m1)  # Only f2, g2 and h2 skipped
         (0, 4)
 
         And once more, not excluding stuff outside m1:
 
-        >>> t = Tester(globs={}, verbose=0, isprivate=lambda x,y: 0)
+        >>> t = Tester(globs={}, verbose=0)
         >>> t.rundict(m1.__dict__, "rundict_test_pvt")  # None are skipped.
         (0, 8)
 
         The exclusion of objects from outside the designated module is
         meant to be invoked automagically by testmod.
 
-        >>> testmod(m1)
+        >>> testmod(m1, isprivate=is_private)
         (0, 3)
 
         """
@@ -1070,7 +1076,8 @@ def testmod(m=None, name=None, globs=None, verbose=None, isprivate=None,
 
     Test examples in docstrings in functions and classes reachable
     from module m (or the current module if m is not supplied), starting
-    with m.__doc__.  Private names are skipped.
+    with m.__doc__.  Unless isprivate is specified, private names
+    are not skipped.
 
     Also test examples reachable from dict m.__test__ if it exists and is
     not None.  m.__dict__ maps names to functions, classes and strings;
@@ -1094,7 +1101,9 @@ def testmod(m=None, name=None, globs=None, verbose=None, isprivate=None,
 
     Optional keyword arg "isprivate" specifies a function used to
     determine whether a name is private.  The default function is
-    doctest.is_private; see its docs for details.
+    treat all functions as public.  Optionally, "isprivate" can be
+    set to doctest.is_private to skip over functions marked as private
+    using the underscore naming convention; see its docs for details.
 
     Optional keyword arg "report" prints a summary at the end when true,
     else prints nothing at the end.  In verbose mode, the summary is

Misc/NEWS

@@ -38,6 +38,15 @@ Extension modules
 Library
 -------
 
+- doctest now examines all docstrings by default.  Previously, it would
+  skip over functions with private names (as indicated by the underscore
+  naming convention).  The old default created too much of a risk that
+  user tests were being skipped inadvertently.  Note, this change could
+  break code in the unlikely case that someone had intentionally put
+  failing tests in the docstrings of private functions.  The breakage
+  is easily fixable by specifying the old behavior when calling testmod()
+  or Tester().
+
 - Closing a dumbdbm database more than once is now harmless (it used to
   raise a nuisance exception on the second close).