add tests for existing behaviour of undef postinc/dec

p4raw-id: //depot/perl@19016

diff --git a/t/op/inc.t b/t/op/inc.t
index f360c03..56d27d2 100755 (executable)
--- a/t/op/inc.t
+++ b/t/op/inc.t
@@ -2,7 +2,7 @@
 
 # use strict;
 
-print "1..24\n";
+print "1..26\n";
 
 my $test = 1;
 
@@ -87,6 +87,12 @@ $b = -$a;
 $b=$b-1;
 ok ($b == -(++$a), $a);
 
+$a = undef;
+ok ($a++ eq '0', do { $a=undef; $a++ }, "postinc undef returns '0'");
+
+$a = undef;
+ok (!defined($a--), do { $a=undef; $a-- }, "postdec undef returns undef");
+
 # Verify that shared hash keys become unshared.
 
 sub check_same {