Added singleton() class param test file

t/78-singleton_class.t

@@ -0,0 +1,47 @@
+use warnings;
+use strict;
+
+use IPC::Shareable;
+use Test::More;
+
+BEGIN {
+    if (! $ENV{CI_TESTING}) {
+        plan skip_all => "Not on a legit CI platform...";
+    }
+}
+
+warn "Segs Before: " . IPC::Shareable::ipcs() . "\n" if $ENV{PRINT_SEGS};
+
+# bad param
+
+my $ok = eval { IPC::Shareable::singleton(); 1 };
+is $ok, undef, "singleton() croaks if no GLUE param sent in";
+like $@, qr/GLUE parameter/, "...and error is sane";
+
+# singleton no exit notice
+
+my ($proc, $warning);
+
+{
+    local $SIG{__WARN__} = sub {$warning = shift;};
+
+    $proc = IPC::Shareable::singleton('LOCK');
+
+    is $proc, $$, "Class param is added if called in IPC::Shareable::singleton() format";
+
+    $proc = -1;
+
+    is $proc, -1, "\$proc set to -1 ok";
+
+    $proc = IPC::Shareable::singleton('LOCK');
+}
+
+END {
+    is $proc, -1, "singleton() on second call doesn't return anything ok";
+    is $warning, undef, "singleton outputs no warnings by default";
+
+    IPC::Shareable::_end;
+    warn "Segs After: " . IPC::Shareable::ipcs() . "\n" if $ENV{PRINT_SEGS};
+
+    done_testing;
+};