1 files changed, 51 insertions, 0 deletions
diff --git a/ext/List-Util/t/readonly.t b/ext/List-Util/t/readonly.t
new file mode 100644
index 0000000000..42ed3d811c
--- /dev/null
+++ b/ext/List-Util/t/readonly.t
@@ -0,0 +1,51 @@
+#!./perl
+
+BEGIN {
+    unless (-d 'blib') {
+	chdir 't' if -d 't';
+	@INC = '../lib';
+	require Config; import Config;
+	keys %Config; # Silence warning
+	if ($Config{extensions} !~ /\bList\/Util\b/) {
+	    print "1..0 # Skip: List::Util was not built\n";
+	    exit 0;
+	}
+    }
+}
+
+use Scalar::Util qw(readonly);
+use Test::More tests => 11;
+
+ok( readonly(1),	'number constant');
+
+my $var = 2;
+
+ok( !readonly($var),	'number variable');
+is( $var,	2,	'no change to number variable');
+
+ok( readonly("fred"),	'string constant');
+
+$var = "fred";
+
+ok( !readonly($var),	'string variable');
+is( $var,	'fred',	'no change to string variable');
+
+$var = \2;
+
+ok( !readonly($var),	'reference to constant');
+ok( readonly($$var),	'de-reference to constant');
+
+ok( !readonly(*STDOUT),	'glob');
+
+sub try
+{
+    my $v = \$_[0];
+    return readonly $$v;
+}
+
+$var = 123;
+{
+    local $TODO = $Config::Config{useithreads} ? "doesn't work with threads" : undef;
+    ok( try ("abc"), 'reference a constant in a sub');
+}
+ok( !try ($var), 'reference a non-constant in a sub');