Unit tests for Vars::detect_release() SWIG bindings

Tests in Python, Ruby, Perl.

It only tests the situation where a release cannot be detected.
To detect an installed release, a system database with the corresponding
installed packages is required.

test/perl5/libdnf5/conf/test_vars.t

@@ -0,0 +1,43 @@
+# Copyright Contributors to the libdnf project.
+#
+# This file is part of libdnf: https://github.com/rpm-software-management/libdnf/
+#
+# Libdnf 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 2 of the License, or
+# (at your option) any later version.
+#
+# Libdnf 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 libdnf.  If not, see <https://www.gnu.org/licenses/>.
+
+use strict;
+use warnings;
+
+use Test::More;
+
+use FindBin;
+use lib "$FindBin::Bin/..";  # Add to search path
+use BaseTestCase;
+
+use File::Spec::Functions 'catfile';
+
+use libdnf5::conf;
+
+
+# test_detect_release
+{
+    my $test = new BaseTestCase();
+
+    my $installroot = $test->{base}->get_config()->get_installroot_option()->get_value();
+
+    # Cannot detect release in nonexistent directory, return undef
+    my $release = libdnf5::conf::Vars::detect_release($test->{base}->get_weak_ptr(), catfile($installroot, "nonexist"));
+    is($release, undef);
+}
+
+done_testing();

test/python3/libdnf5/conf/test_vars.py

@@ -15,10 +15,21 @@
 # You should have received a copy of the GNU General Public License
 # along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 
+import os
+
+import libdnf5
+
 import base_test_case
 
 
 class TestVars(base_test_case.BaseTestCase):
     def test_getting_undefined_variable(self):
         vars = self.base.get_vars()
         self.assertRaises(IndexError, vars.get_value, "undefined")
+
+    def test_detect_release(self):
+        installroot = self.base.get_config().installroot
+        # Cannot detect release in nonexistent directory, return None
+        release = libdnf5.conf.Vars.detect_release(
+            self.base.get_weak_ptr(), os.path.join(installroot, "nonexist"))
+        self.assertEqual(release, None)

test/ruby/libdnf5/conf/test_vars.rb

@@ -0,0 +1,33 @@
+# Copyright Contributors to the libdnf project.
+#
+# This file is part of libdnf: https://github.com/rpm-software-management/libdnf/
+#
+# Libdnf 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 2 of the License, or
+# (at your option) any later version.
+#
+# Libdnf 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 libdnf.  If not, see <https://www.gnu.org/licenses/>.
+
+require 'test/unit'
+include Test::Unit::Assertions
+
+require 'libdnf5/conf'
+
+require 'base_test_case'
+
+
+class TestVars < BaseTestCase
+    def test_detect_release()
+        installroot = @base.get_config().get_installroot_option().get_value()
+        # Cannot detect release in nonexistent directory, return nil
+        release = Conf::Vars::detect_release(@base.get_weak_ptr(), File.join(installroot, "nonexist"))
+        assert_equal(nil, release)
+    end
+end