Dpkg::Vendor: Add test cases for get_vendor_dir()

scripts/t/Dpkg_Vendor.t

@@ -16,9 +16,12 @@
 use strict;
 use warnings;
 
-use Test::More tests => 5;
+use Test::More tests => 6;
 
-use_ok('Dpkg::Vendor', qw(get_current_vendor get_vendor_object));
+use Dpkg;
+use_ok('Dpkg::Vendor', qw(get_vendor_dir get_current_vendor get_vendor_object));
+
+is(get_vendor_dir(), $ENV{DPKG_ORIGINS_DIR}, 'Check vendor dir');
 
 my ($vendor, $obj);