Added test_print.py. I want to have a test suite when the print function is backported to 2.6 as a future import.

Lib/test/test_print.py

@@ -0,0 +1,102 @@
+"""Test correct operation of the print function.
+"""
+
+import unittest
+from test import test_support
+
+import sys
+import io
+from contextlib import contextmanager
+
+NotDefined = object()
+
+# A dispatch table all 8 combinations of providing
+#  sep, end, and file
+# I use this machinery so that I'm not just passing default
+#  values to print, I'm eiher passing or not passing in the
+#  arguments
+dispatch = {
+    (False, False, False):
+     lambda args, sep, end, file: print(*args),
+    (False, False, True):
+     lambda args, sep, end, file: print(file=file, *args),
+    (False, True,  False):
+     lambda args, sep, end, file: print(end=end, *args),
+    (False, True,  True):
+     lambda args, sep, end, file: print(end=end, file=file, *args),
+    (True,  False, False):
+     lambda args, sep, end, file: print(sep=sep, *args),
+    (True,  False, True):
+     lambda args, sep, end, file: print(sep=sep, file=file, *args),
+    (True,  True,  False):
+     lambda args, sep, end, file: print(sep=sep, end=end, *args),
+    (True,  True,  True):
+     lambda args, sep, end, file: print(sep=sep, end=end, file=file, *args),
+    }
+
+@contextmanager
+def stdout_redirected(new_stdout):
+    save_stdout = sys.stdout
+    sys.stdout = new_stdout
+    try:
+        yield None
+    finally:
+        sys.stdout = save_stdout
+
+# Class used to test __str__ and print
+class ClassWith__str__:
+    def __init__(self, x):
+        self.x = x
+    def __str__(self):
+        return self.x
+
+class TestPrint(unittest.TestCase):
+    def check(self, expected, args, *,
+            sep=NotDefined, end=NotDefined, file=NotDefined):
+        # Capture sys.stdout in a StringIO.  Call print with args,
+        #  and with sep, end, and file, if they're defined.  Result
+        #  must match expected.
+
+        # Look up the actual function to call, based on if sep, end, and file
+        #  are defined
+        fn = dispatch[(sep is not NotDefined,
+                       end is not NotDefined,
+                       file is not NotDefined)]
+
+        t = io.StringIO()
+        with stdout_redirected(t):
+            fn(args, sep, end, file)
+
+        self.assertEqual(t.getvalue(), expected)
+
+    def test_print(self):
+        def x(expected, args, *, sep=NotDefined, end=NotDefined):
+            # Run the test 2 ways: not using file, and using
+            #  file directed to a StringIO
+
+            self.check(expected, args, sep=sep, end=end)
+
+            # When writing to a file, stdout is expected to be empty
+            o = io.StringIO()
+            self.check('', args, sep=sep, end=end, file=o)
+
+            # And o will contain the expected output
+            self.assertEqual(o.getvalue(), expected)
+
+        x('\n', ())
+        x('a\n', ('a',))
+        x('None\n', (None,))
+        x('1 2\n', (1, 2))
+        x('1*2\n', (1, 2), sep='*')
+        x('1 s', (1, 's'), end='')
+        x('a\nb\n', ('a', 'b'), sep='\n')
+        x('1.01', (1.0, 1), sep='', end='')
+        x('1*a*1.3+', (1, 'a', 1.3), sep='*', end='+')
+
+        x('*\n', (ClassWith__str__('*'),))
+
+def test_main():
+    test_support.run_unittest(TestPrint)
+
+if __name__ == "__main__":
+    test_main()