Bug 42551: Add unit test

Signed-off-by: David Nind <david@davidnind.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Pedro Amorim <pedro.amorim@openfifth.co.uk>

t/db_dependent/Koha/Plugins/C3.t

@@ -0,0 +1,47 @@
+#!/usr/bin/perl
+
+# This file is part of Koha.
+#
+# 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 <https://www.gnu.org/licenses>.
+
+use Modern::Perl;
+
+use Test::More tests => 1;
+
+use File::Spec;
+use FindBin  qw( $Bin );
+use IPC::Cmd qw( run );
+
+use C4::Context;
+
+my $plugin_class = 'Koha::Plugin::1_CalcFineEmpty';
+my $plugins_lib  = File::Spec->rel2abs("$Bin/../../../lib/plugins");
+my $plugin_file  = "$plugins_lib/Koha/Plugin/1_CalcFineEmpty.pm";
+
+my $dbh = C4::Context->dbh;
+$dbh->do(
+    q{REPLACE INTO plugin_data (plugin_class, plugin_key, plugin_value) VALUES (?, '__ENABLED__', '1')},
+    {}, $plugin_class
+);
+
+my ( $success, undef, $full_buf ) = run(
+    command => [ $^X, "-I$plugins_lib", '-c', $plugin_file ],
+    timeout => 30,
+);
+
+$dbh->do( 'DELETE FROM plugin_data WHERE plugin_class = ?', {}, $plugin_class );
+
+ok(
+    $success,
+    'perl -c on an enabled plugin file does not trigger a C3 merge error'
+) or diag( join( '', @{ $full_buf // [] } ) );