Bug 10325: (follow-up) add test for overriding system preferences

To test:

[1] Verify that prove -v t/db_dependent/sysprefs.t passes.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>

t/db_dependent/sysprefs.t

@@ -1,9 +1,32 @@
 #!/usr/bin/perl
 
+# This file is part of Koha.
+#
+# Copyright (C) 2012 BibLibre SARL
+# Copyright (C) 2013 Equinox Software, Inc.
+#
+# Koha is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# Koha is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Koha; if not, see <http://www.gnu.org/licenses>.
+
 use Modern::Perl;
-use Test::More tests => 2;
+use Test::More tests => 3;
 use C4::Context;
 
+# Start transaction
+my $dbh = C4::Context->dbh;
+$dbh->{RaiseError} = 1;
+$dbh->{AutoCommit} = 0;
+
 my $opacheader = C4::Context->preference('opacheader');
 my $newopacheader = "newopacheader";
 
@@ -12,3 +35,12 @@ ok(C4::Context->preference('opacheader') eq $newopacheader);
 
 C4::Context->set_preference('opacheader', $opacheader);
 ok(C4::Context->preference('OPACHEADER') eq $opacheader);
+
+$ENV{OVERRIDE_SYSPREF_opacheader} = 'this is an override';
+C4::Context->clear_syspref_cache();
+is(C4::Context->preference('opacheader'),
+   'this is an override',
+   'system preference value overridden from environment'
+);
+
+$dbh->rollback;