gh-74678: Increase base64 test coverage (GH-21913)

Ensure the character y is disallowed within an Ascii85 5-tuple.

Co-authored-by: Lee Cannon <leecannon@leecannon.xyz>

diff --git a/Lib/test/test_base64.py b/Lib/test/test_base64.py
index fa03fa1d61ceabb703ffc7e29ae1e7310c2e180c..f6171d3ed4efd7328d4df31ec2c6dc9c332a272d 100644 (file)
--- a/Lib/test/test_base64.py
+++ b/Lib/test/test_base64.py
@@ -586,6 +586,7 @@ class BaseXYTestCase(unittest.TestCase):
         eq(base64.a85decode(b'y+<Vd', foldspaces=True, adobe=False), b' '*7)
         eq(base64.a85decode(b'y+<U', foldspaces=True, adobe=False), b' '*6)
         eq(base64.a85decode(b'y+9', foldspaces=True, adobe=False), b' '*5)
+        eq(base64.a85decode(b'aaaaay', foldspaces=True), b'\xc9\x80\x0b@    ')
 
         self.check_other_types(base64.a85decode, b'GB\\6`E-ZP=Df.1GEb>',
                                b"www.python.org")
@@ -689,6 +690,8 @@ class BaseXYTestCase(unittest.TestCase):
         self.assertRaises(ValueError, base64.a85decode, b's8W', adobe=False)
         self.assertRaises(ValueError, base64.a85decode, b's8W-', adobe=False)
         self.assertRaises(ValueError, base64.a85decode, b's8W-"', adobe=False)
+        self.assertRaises(ValueError, base64.a85decode, b'aaaay',
+                          foldspaces=True)
 
     def test_b85decode_errors(self):
         illegal = list(range(33)) + \